mercedeswannabe

hey guys, im new here and new to mercedes, i have a 1994 c280, the fellow i bought it from changed the head gasket, ran perfect before that, there are no leaks, engine runs like the timing is severely retarded, no power, hard to start, all cylinders firing, and i installed new plugs, being new to this, i dont know what to do, my instincts tell me he timed it improperly, if so, i dont know how it times or where to start, bought this for my wife, beautiful car, sure would like to have her drive it without me pushing! can someone take me for a walk through this and possible probs? sure would appreciate it.