First of all I would like to thank those that helped me solve my A/C problems. My dual heater valve was toast!

I have been offered a 1995 E320 with a blown head gasket.
What could have caused this situation? What could potentially be bad that would need to be addressed/fixed?
What all is involved with replacing a head gasket? Do you need to be a "mercedes" mechanic? Remove and machine head and valves; is this all that is involved with this operation?

or should I pass on this car? Perfect condition just has the gasket problem. This car even looks to be in better condition than my own e320!
thanks in advance
Pedro