Separating fact from fiction in that thread was not fun. I don't think the "30 minutes" estimate includes reading time there.

But it is possible. I did it. Following are my notes taken back in the day, soon after doing it. I did not do it this way for speed reasons, but because I did not want to rely on separating the outer end of the axle from the hub, etc. My general experience with axles is that they are easy until you run into the simple step that turns out being impossible. So having workaround methods can save you.

This is for my 2001 3.0i E53. Was written for my own notes (for next time), so refers to my own specific tools in some spots.

On 12/21/19 did both boots on left front of x5. If knowing both boots will be replaced, I think this is the best way to do it, without chance of getting stuck.

If I am SURE I want to leave the inner joint/boot untouched, it may make sense to try to pop out the outer joint.

Things not touched: axle nut, brakes, outer CV joint/axle (other than the boot, and wiping away grease; i.e., the splined axle end is not pulled out from the joint)

Jack up front end, both sides on jack stands (opposite side up, just in case need to rotate opposite wheel - not needed in this case). Wheel off.

Remove inboard end of lower control arm. 16mm bolt head, 18mm nut. When reinstalling, 100Nm + 90*. This was the only bolt/nut removed in the whole process.

Turn steering wheel all the way to whichever side is being worked on - moves tie rod (in front of axle) all the way out, creating space.

All clamps and old boots will need to be removed. Can do all now. At a minimum now, remove the inner boot's big clamp, pull the boot off at that end, wiping any grease that spills out.

Pull knuckle outboard as far as convenient (it will want to spring back), bracing it from returning using the adjustable Lisle hood prop ; 45900 HOOD PROP ; https://www.lislecorp.com/specialty-tools/hood-prop

While doing that, pull the inner CV joint tripod out of the housing.

Wipe off grease from exposed inner CV joint.

Remove retaining ring on inner end of the tripod, using Craftsman Professional Retaining Ring Pliers 009-47386. On the right side, the tripod assembly was stuck, would have required removal with a small 3-jaw puller. On the left side, it was loose, moving freely even before the retaining ring was removed.

Tripod can then slide off (gear puller if needed) the end of the axle shaft. When reinstalling, the flatter of the two sides goes against the retaining ring.

At this point, I made some weak attempts to pop out the axle shaft from the outer CV joint, but it would not come, so ...
And this is why this is my preferred method - it completely avoids any risk of the outer CV's c-ring being stuck. The tradeoff is that the tripod may be stuck, but if so, there is easy full access to it, and it can be removed using a gear puller, rather than hammering and hoping the c-ring is aligned and not stuck deep in the rectangular groove of the splined axle end.

Cut / slide / remove all boots and boot clamps. Wipe everything as clean as possible.

So at this point, the outer CV joint is fully intact, with the axle still in it. The inner CV joint's tripod assembly has been pulled off. The inner end of the axle can be freely moved around due to all the space created by steering the tie rod to the outside, and using the hood prop tool to hold the knuckle out.

Slide on new boots + clamps, all in correct order.

Tripod on, oriented so the flatter of the two sides goes against the retaining ring. Retaining ring back on.

80g grease in each boot, clamps in place but not tightened.

Not sure if necessary, but at this point, before final clamp tightening, I jacked up the brake rotor so the suspension was level (just as the chassis begins to lift off the jack stand), and re-connected the control arm + bolt (100 Nm + 90*).

With the suspension leveled here, I made sure the boots were not pre-stressed or pressurized with air, then pinched all clamps using my Knipex 2-way Oetiker clamp tool.

The quickest and easiest (as long as you have the tools) is to leave the inboard side of shaft alone and pull just the outer joint portion with the special tool. I don't know who did the write up for that but I am pretty sure it's on here somewhere.

Late reply, but I finally got some work done on the X5 today. While I was at it I put some calipers on the front axle just inboard of the outer CV boot clamp and came up with 27 mm. The new outer boot I have waiting to be installed is just a hair under that (ID), and seems to be a harder, more plastic-ish rubber. They are OE BMW boots that I bought for the job.

Oddly there is only one part number on one of the two boxes, (31607565315) which RealOEM says is the inner repair kit. The other box contains the outer repair kit, but no PN. The one sticker also says GKN on it.

I think the the inner boot is the same for both A and B axles. So you ordered a "kit" with both boots for your 2002 and the outer boot (with no part number) is the harder one and the original is soft?

Was trying to add to the discussion of if there were two different axle sizes and corresponding boots, part numbers, etc. I figured I’d measure my axle and boot kit since I had them handy.

Assuming you have factory axles, just count the ridges on the CV boot as I mentioned above: 4 vs 5

Just turn one wheel all the way R or L.
Turn off engine, get down on your knees with a flash light to count the ridges.

Yes, I think it would be cool if the differences and part numbers between the boots and shafts/axles could be sorted so maybe people can have the option to switching to the hard boots or even the type "B" axle if they order new axles.

I’m finally putting this job on my calendar for next week. I’ve put it off for several months since I discovered the left outer boot split and throwing grease. It failed where the small boot clamp goes around the axle.

Word to the wise, I took a look at the “kit” I bought from FCP and realized they don’t include an axle nut. Sort of surprised at this, but then again, I didn’t read the description closely enough when I ordered. Two nuts now in route as I’ll also need to do the right side in the not so distant future. Hopefully some heavy duty RV tape can extend that boots life a bit.

My initial thought was to do both inner and out boots on the left side as long as the axle was coming out. However, since it seems after reading the above that can just do the outer boot without pulling the whole axle, I’ll take a good look at the inner and decide when I’ve got it up on the lift. I did break down and buy a good press to push the axle out of the carrier, amd the special tool to pull it back in so the whole exercise should hopefully kill far fewer brain cells. I’ll knock out an oil change while the x is on the lift.

Which tool is it that you bought? This job is in my future too

I'm not sure what he means by "a good press to get the axle out" but there is a thread or two on here describing the process and tools that make it easier. I have noticed they sell the tool to pull the axle back in through the hub on Ebay and Amazon now so that's a bonus.