The selection of the 28 versus 35 should also consider how you drive.
Do you do mostly city driving? If so I would go for the 35. Far more fun and you don't have to hear the pesky diesel chatter of the n20 turbo 4...I don't... but some find it loud and annoying at stop lights.
If you do hwy like me 90% of the time go with the 28. Gas milage is very good. I have gotten as high as 38 in f30 and 32 in f25 loaner cars on my daily all fwy no traffic 120 mile rt commute.
As for purchase how are you at negotiating? I love that part and confidence rules, just remember the BMW buying experience isn't the same as with Chrysler or GM. You will be treated with respect. If not walk.
Here are my rules for buying;
1) always be closing...meaning be confident about you offer, calculator in hand, know your options in advance and always have end game in sight
2) focus on final purchase price of $500 over invoice. Never get bogged down in payments. Always stop the sales person and remind them that heck you might pay cash.
3) if necessary only give them one chance to talk to boss and tell them next time you talk to boss.
4) always negates price, loan and trade in separately! This is key!
5) never purchase what the loan/paper work guy is trying to sell you! No...the wheel and tire insurance is not worth it!
6) car is made in Spartanburg, NC. Yes end of year is feasible.