These forums are an invaluable resource. An example I have was when working on a friend's W210 with a transmission issue. He had taken it to a local, trusted indy shop who said it was toast and needed a rebuilt/used transmission. One quick search on Benzworld and I found it was likely just a broken return spring for the main pressure valve. Sure enough, that $5 spring was the culprit, and replacement only required dropping the pan and removing a few small bolts holding its retainer plate on the side of the valve body.