I would start by posting this question at E90post...you'll get a lot more feedback over there as there's a lot more traffic...and E90 owners.
http://www.e90post.com/forums/index.php
Most stuff is fixable - I would make sure you buy one that has the packages/options that you want as most of those are difficult and expensive to add later. And make sure you get a PPI done - those would be my recommendations to start.