Regarding modifications - few years ago a new law was passed specifically to reduce the amount of modifications required - it accepts clusters showing both miles and km and US-standard bumpers (which are softer). The only thing that '10 M3 would not pass is DRL (you should not be able to disable it, which you can on US car). But as far as I know they do not check it during the inspection. So if you turn on DRLs in the computer before the inspection, you will very likely pass without any modifications (I did, and several other people on the forum did as well:
http://www.e90post.com/forums/showpo...8&postcount=19). If you do not pass, there is no penalty AFAIK, and they will tell you exactly what needs to be changed, so you may end up making less changes than you planed (e.g. no change to cluster but only DRL reprogram). My point is try to pass the inspection before you modify anything.