Recently purchased 1991 420sel with 170k. My local MB mechanic confirms that the reason I get a big puff of light blue smoke at startup and continous smoking is because the valve stem seals are worn. Maybe one, maybe all. I can do this myself and would like to do it without removing the heads but just taking the valve covers off. In addition to the seals and springs what else do you recommend that I replace while I'm in there. I'm a novice but mechanically inclined with tools. I suspect I could do lifters and I've heard talk about rails and tensioners. This is not a daily driver, so I have time. I just want to replace the easy things under the covers while that part of the car is open.
BTW the car runs good, it just smokes.