I have a 93' 500SEL with 140K miles on it. It has developed a bad misfire on a few cylinders, and has no power from the starting line. It takes forever to get up to speed, but runs Ok once there. It has been suggested by my mechanic (He knows I am a DIYer) and people on this forum to start with a tune up and maybe the 2 coils behind the drivers headlight. I replaced the D-caps, rotors and plugs. The plug wires looked Ok, and who wants to pay $250 for a set of wires. The caps had the green oxidation, and the plugs weren't terrible. This provided no change. Next is the coils. Is there an easy way to check them. I can't even seem to get the covers off. Is there a trick to it? I have weakly tried to pull up on them, but don't want to force anything. Also, is there an easy procedure in taking them out. The one in back seems to be right behind the headlight. I can't even get my hand back there. Do I have to take out the headlight? I am thinking of having my indy do it.

Thanks in advance