I replaced the compressor last night, it was pretty easy overall.

I didn't see any DIY posts mention it for the e53, but I took the fan and fan shroud out and it made everything much easier to access/work around. I think I actually ended up doing everything from above.

I put 50mL of PAG oil in. I drained the old compressor and probably got about 30mL out. I found somewhere that BMW recommends adding at least 50 mL with a compressor replacement, so I decided to do that. I used PAG 46 as that is what both the old and new compressor had a label saying to use.

I did not replace the drier, as I only had it open a short time. The shop can't get me in to recharge it until Monday, so I'll probably end up replacing the drier over the weekend.