Since I am new to BMW I am not familiar with all the different Chassis designations E34, E36, E39 etc... Can someone guide me as to what years are 'good' for the 540i, and what years 'need more attention'.

I see some very reasonably priced cars...What should I be looking for in my USED bimmer, and what should I avoid. I like the idea of a good sized sedan offering excellent performance and good durability...at the same time not impossible to work on...

Thanks in advance