For what it's worth, I will echo the sentiment from X5SND above. I wish you well if you are getting rid of it, but if you bought the E53 and expected Toyota/Volvo reliability, it was a wrong assumption.
The E53 is a GREAT vehicle (many of us on the forums are on our 2nd or 3rd E53), and personally I don't see myself driving anything else for a long time, I've already owned mine for 2 years.
Was it a pain in the ass getting caught up on all the maintenance needed on a 10 year old vehicle? Hell yes it was. Was I a little annoyed at times, of course. When you buy a used vehicle though you better expect the most amount of problems and "catch up" maintenance in the first 2 years of ownership. I've had a few months (about 6 actually) now with literally not a peep from my X5, it just goes.
But to start off my list, when I bought it, I had to do the following:
-Air bags in the front and air compressor (known for leaks esp at 10 years old!)
-Belts, tensioners, fan clutch was shot (belts and tensioners were preventative)
-Driveline fluids replaced (PS fluid, brake/clutch flush, front/rear diffs, transfer case fluid, manual trans fluid)
-Complete rebuild of front suspension (CV boots, front wheel bearings, thrust arms, wishbones, ball joints, tie rods, front sway bushings), and some rear susp I did myself (rear sway bar links and bushings), and 4 wheel alignment
-New set of tires as original 10 year old Michelins were dry rotted and bald, I elected to upgrade to staggered 20s with Toyos
And on top of that the slight mods I did (I won't list those as its not relevant), and some minor fixes like passenger door carrier, weatherstrip clips, HVAC buttons, etc.
Basically besides the front wheel bearings, those were all things I was expecting to have to do soon after taking ownership of a 10 year old vehicle in the Northeast. Anything with rubber in it or a rubber bushing is going to break down regardless of mileage (I have 71k now, bought my X at 58k), fluids need periodic replacement, and wear items like belts, etc heat cycle. These are my experiences, but now that I am "caught up", other than every day paying attention to how the vehicle drives and behaves, I will go by a periodic maintenance schedule for other items.
The E53 has plenty of its share of quirks, which are well documented thankfully by the many members here. However, the drive of the vehicle, the way its planted, I can't see myself driving anything else. My mom drove a Q7 S-line TDI, and while the engine is beautiful and mileage great, the E53 truly sucks you in as a real driver's vehicle, whereas the Audi felt boring and disconnected from the road.
How many other examples of a 14 year old design do you see on the road each day that still excite you? You'd be hard pressed, and although yes the E53 is 14-15 years old now, it's still a vehicle that people mistake for something much much newer! Not many others like it IMO.
Since you bought the car new and list these as your major problems of ownership in 122k miles, I'd like to note the following:
- Sunroof cassette @ $3500 (not repaired) (Both repair kits can put the panoramic sunroof in working order, $250 in parts but if you are paying the dealer for everything I'd expect them to charge 1k in labor, still cheaper than the whole cassette replacement you paid $3500 for)
- Replacement of all electronics in "money corner" as the dealer puts it. Back left corner due to sunroof drain plugging. $3600. (sunroof drains clogging are very common, you didn't notice water pooling up prior to all electronics being damaged? Its a shitty situation, but normally the vehicle gets musty with standing water)
- Pixelated dash (not repaired) (both MID and cluster can be repaired with new cluster ribbons for $200 by a pro, or $60 if you DIY, as tmv has done)
- Auto wipers and headlight sensor failure. BMW says replace the windshield for $1300. (was your windshield ever replaced? if its original, I would say you it might be a recode of your DME module, but if just auto wipers and auto headlights don't work, you can still use wipers on regular cycle and manually turn on headlights, right? Not exactly a disasterous failure, I never use auto headlights)
- CV joint failure (boot ripped? very common and needs replacement every 50k miles or more in a salt prone area)
- Power steering pump replacement (not common, but has been documented)
- Thermostat replacement (very common, surprised you only did 1 T-stat replacement!)
- Passenger mirror failure (the dip function? easily fixable in an hour with no money and just hand tools)
Honestly, for original owner over 8 years and 122k miles, your list isn't too bad LOL