It's not a difficult job just be sure to keep the parts with their respective cylinders. Also, I was told to be sure to use OE lifters. I replaced mine with 225K on the clock but I still periodically have noise on startup (switched to Mobil 1 15W-50 and still does it). I thought that perhaps the housing that the lifters fit into were worn but you could still see the crosshatch pattern on these. I guess the preload needs to be adjusted which I may get around to doing some day (like when I repair the leaking head gasket). Oh, you should hear the lifter leakdown on the 112/113 engines---my '01 E55, '01 E320 and '04 SLK32 all did/do it and it's truly awful. I don't understand how MB can't get this right. Mark