I'd replace the seal if you've got the transmission out. I think the earlier M103's, there is an updated seal carrier. You need to talk to a good MB parts guy.
Service seal is for a damaged(worn) sealing surface. Chevy's they use to sell a seal where the lip was moved about 0.063", so it was on a new part of the crank hub. A little bigger works too.
No reason you'll need it. best of luck,
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD