617's are like cockroaches, they're everywhere! Ask nicely in the "Want to Buy" section of this site, and you'll probably be able to pick one up pretty easily.

When I had my 603's head redone 2 years ago, it ran me right at $400. I had all 12 valve guides replaced and the valves all re-ground. My seats and valves were still good enough to be re-used and the head did not need skimming.

Are you capable of performing the head gasket job yourself, or will you be paying a shop to swap the head? If you're paying a shop to do it, expect a staggering bill - it is not a trivial task.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]