The hoist isn't really necessary. I had my 15 year old daughter help me lift off the head (head w/intake attached, exhaust manifolds removed) with no problems or strain at all. I even gave her the heavy side! I put it back in by myself (just the head w/out any manifolds). Putting the manifolds back on with the head bolted down was no problem at all either, with a few components removed for access, a long extension and a swivel socket for a few of the harder bolts.
Mine was a 300E, I have a 190E 2.6 also, it looks a little tighter, but I would be surprised to find that it couldn't be done the same way.

I think ps2cho is right about where I would guess too, $1200-1500 at a GOOD indie who knows some Mercedes. Another good estimate posted above, about $550-650 in parts, and machine shop work doing it yourself.