1. Yes
2. Dealer will have the most info. there are recalls and extensions on various parts. they will know if these have been fulfilled.
3. All a matter of perspective. I personally do not like the way the xdrives handle, but if you've driven it and cant tell a difference from RWD then by all means.
4. Goes without saying
I started with a JB4, then went to JB4 BEF, then left JB4 and went MHD. You will want to search this but I could have saved a few bucks and a lot of headaches if i went MHD to begin with... thats if they where around back then.
5. no input
6. Depending on what youre paying, resale may or may not be a factor. Im really interested in what the market will look like for a clean e9x 335i 5 years from now. That said, a high mile BMW is a hard sale.
7. If its in the cards get a warranty. Parts are very expensive and labor is insane. I would not be able to afford this car if I couldnt do my own work.
PPI would be a good investment. Oil leaks, bad or failing turbos, injector issues, fuel pump/s, coil issues, these are all things that will need to be looked at very closely. The 335i is an amazing car, but its a diva.