Are you sure you just don't need to replace the chain tensioner? What noises, if any, do you hear?
I'd recommend spending the dough on a dealer or good indy that would warranty the work because with parts and labor its not that cheap to do....and if you've never done one on a M119, it could be daunting once you get in there. But go for it if you are a good wrench and confident that it'll go OK.
