The paint, upholstery, chrome, trim, etc. on a Benz hold up EXTREMELY well as compared to other cars. If you're not experienced with the breed, most any old MB will LOOK to be in great shape.
The coolant oil mix could be caused by problems other than a headgasket. If the previous owner did not keep coolant changed as they should, corrosion in the aluminum head can lead to the same symptoms. Also a crack can lead to it.
Most likely the problem is head related. It might be worthwhile to pressurize the cooling system with a tester and check for bubbles in the coolant. Likewise pressurizing each cylinder in turn with a leakdown tester could point out the problem.
Changing the head is a project, but if you are accustomed to twisting bolts it should be no problem.