I've done this job and it's not fun. You will need the proper tools - either the quality factory items that work on a lot of different engines ($500+), or the Sir Tools junk that only works on a few engines including the 603 ($225). If you're not getting blue smoke out the exhaust after extended idling, and don't have unusual oil consumption, I suspect the seals might be OK (although it's not a bad idea to replace them regardless). You absolutely want to use the OE dealer "genuine Mercedes" valve stem seal kit - NOT the aftermarket kit!!
