well, since you have a 20xx X5 with the x.x engine, I strongly recommend to use 'z' as the spark plug changing procedure...fill in the x's and the 'z' will become self evident via the search function.

You don't need to replace the plugs until about 100k miles, per BMW's schedule for my N62 4.4i on my 2005 X5, but I did it at 64k-ish chasing a misfire.

Concur on buying the Bentley manual. Money well spent especially when you have limited experience...

attempted mine today.as far as difficulty goes its not hard at a glance.however when i did mine the 3 coils towards the back of the engine refused to come out(02 X5 3.0i).i think ill take another crack at those 3 when i have the time.car seems to be running fine even tho half the plugs are new and the other half are old.i went Bosch platinum 4+ simply because my nice baby deserves nice things:D

mother of god haha,
i just removed my spark plug (well one to check it) and putting it back in was a huge pain in the ass. i just think cause my spark plug socket is so damn snug. what a chore

I have the same engine in my 545i and I don't change plugs until 100k. 78k on them now.

I use a magnetic spark plug socket instead of one of those old fashion rubber thing socket make the job super easy.

Plug replacement on the 4.8is is REAL Easy. Takes approx 1 hr including cleaning up the covers and tools when finished.
It only takes a little patience and simple hand tools (sockets, assort of extensions, a plug starter/gab tool (See Tooltopia:http://www.tooltopia.com/_img/THX/THX492.jpg), and a few different sized ratchets handles for clearance) oh and a fender cover as you will half in the engine bay at times.

Those of you who have the replaceable boots on the coils should replace them at plug replacement time. Think of them as spark plug wires as that is their purpose; to transfer the voltage to the plug from the coils. In BMW with coil on plug ignitions, there are one coil per cyl hence one boot per cyl. These "boots" build up resistance over time and will create coil failures as the resistance builds to the point of miss fires at acceleration/ high loads. On the replaceable boot coils, they just twist and pull off. The one piece coils DO NOT have removable boots.

Attached images are of the two types of coils found in our SAVs and the 2003 plug chart. I would also recommend a review of the NGK website for the latest and greatest plug recommendations as technology moves forward since production dates. NGK Spark Plugs USA This site will provide the plug manufacturer's recommendation for your application. I noticed some re-sellers having old applications recommendations on their websites, so read a lot before ordering the plugs.

I went with the ZFR6FIX-11 Iridium IX, at 50K - 9 years, and noticed an improvement in tip in acceleration and idle quality. All very typical for fine wire precious metal plugs. This technology wakes up older vehicles as well, as those vehicles run a little lean or rich depending on the year of production and emissions technology used at the time. On old big block V8 US muscle cars it is worth $$ for the improvement in idle and tip in throttle improvements.

I'm no help on the 8 cylinders, but I changed the plugs on my 3.0L at close to 110k miles. One benefit: improved fuel mileage, maybe 1 mpg or so. Easy DIY, done coincident to trickier, but doable, tasks: replacing 02 sensors [all four] when one started throwing a code, and replacing the valve cover gasket ['VCG'] to fix an oil leak. I think the conventional wisdom [perhaps fed by dealers ....] is that bimmers are difficult for DIY'ers. Not so, particularly in this modern, internet era, when lots of helpful info [including videos and pictures] are posted. In addition, if you don't work with your hands for a living, its great therapy!

go on ebay and see if you can score a spark plug bmw tool. Honestly, it's the best tool to do the spark plugs from my experience. Yes, the sockets are great and you can get in there, yadi yadi but this tool is single piece so there's no tool to get stuck on the spark plug.

It really is really easy to do the spark plugs on the M62's.... but you're on an N motor so i'm not 100% sure if it's the same as just taking plugs off, unscrew, screw plug back and done.