Are you looking at a 98 M3 or M-roadster? My 98 M3 with 64k has been running well. Besides wear and tear parts, other non-warrantee work includes:
Rear shock tower replacement - both sides
Leak at lower pressure end of power steering pump hose
My wife's 99 M-roadster with 47k (other than wear and tear items) has been rock solid.
that's it!