The answer to that depends on where you live.

If you're in a high $$ area like LA, labor gets steep vs. somewhere else.

You will need to call around your area for estimates.

I would call a few local MB dealers and maybe a few local independent shops and ask who they use for machine shop work. You don't want a guy who's done nothing but Fords & Chevies working on your MB head.

Find a shop that's done a lot of euro car work.