450 gl

Just been told i didnt keep a paper trail on my 2007 GL450 with 32000 miles after light kept coming on they pulled the engine loosing compression on three cylenders scratches in cylender wall i saw them told me 2100 or 41000 out of my pocket i could not proove service was done properly and they didnt know why cylenders loosing pressure car scattered all over the the dealers shop or if i buy the gaskets they will put it back together like it was that they dont make mistakes with their cars engins well maby this is the first service was done using parts and oil mb recomendes but i can only prove too of them and you guys think you have trouble over a barrel know where i can get a used engin? Bob