i just did my cylinder head on my 88 300se .. cost me about 450 including gasket set. my cylinder head was pressure tested for cracks and the valves were done too that cost me 290. my gasket set was 140.00 .. all in all pretty easy to do and well worth it .. i have 190k miles on it (luckily only two owners previously and old grandpa and then a school teacher). runs great

and yes i raced this around for about a year and blew my head gasket .. white smoke out exaust.. best bet is to repair it asap instead of risking any damage to other parts .. mine was so bad i had water running out of my exhaust. try and listen for air leak (sounds like a car on the jetsons cartoon) keep an eye both on your temps and water level. also checking your oil regularly