Thanks for the great reply. I'll probably get a set of OEM Ina lifters and return them if not needed. Machine shop seemed keen to handle any issues with valves. I'll cough up for Merc valve seal set per your recommendation.
Not a snap-on, but this looks like the right tool for the cylinder bolts and $40 for delivery in 2 days from NY:
Assenmacher Specialty Tools 12 Pt Cylinder Head Bolt Socket - Toyota, VW, Audi, Mercedes 10mm
140mm Long.
Used for Removal and Replacement of cylinder head bolts.
Applicable to OM 601, OM 602, and OM 603
Snap-on catalog gives me a headache.
I finally bumped into directions from site (courtesy gsxr):
http://www.w124performance.com/service/w124CD1/Program/Engine/602_603/01-5800hx.pdf
Looks like with this tool one can avoid removing the camshaft and camshaft towers (Parroting this). The bolt sequence is impossible to see in the pdf. Attached legible image.