I learned that same lesson with my dozer. Before buying, I found several mechanics who said they would come out if something happened, but when something happened, they never showed up. Eventually it turned into a couple of months of calling and waiting, asking around for other mechanics, then calling and waiting some more. Eventually I just decided to figure out how to do it myself. So far, since then, I've bought a lot more really big wrenches and sockets, and managed to figure it out.
What's wrong with your excavator?