I recently had a head gasket replaced on my '91 300E by a dealer. The labor charge was about $1,400 and included checking the head and valves (perfect, no work needed).
I only have 56K on it so the only thing that needed to be done besides the gasket was a new serpentine belt.
I have the peace of mind that the work was done by highly experienced people and backed up by a dealer with a sterling reputation. Compared to the cost of a new car, $1,400 is peanuts.