Well, first off, the recent junkyard engines that I have seen used by people in this forum seem to have turned out pretty good. Also, junkyards around here give generous warranties on their parts. Second, replacing a few parts in your engine in your backyard does quality for being called a "rebuild". Third, I would say the odds that a backyard major engine repair turns out a total success are at best 50-50. There is alot more to being a professional mechanic than people who are not would care to admit. There is more to a "rebuild" than just slapping a set of rings and a rod in, while laying in your driveway, drinking a beer, and then hitting the ignition. It is really amazing that I see people who have major concerns about using the proper fluids, approved by VW in their TDI. However, when it comes to a computer controller state of the art diesel engine, heck, anybody can work on it. And, someone with no engineering education, they can change the factory operating perimeters in the computer, as they know more the the engineers who created it. Absoulutely amazing how ignorant we have become, and in such a should period of time.