You are right, as a learning experience it is a LOT better to take old parts out of the car, clean them up, find repair kits or whatever to fix them up, and put them back in. Maybe several times. It can also be a lot cheaper. It DOES take a lot more time but when you are through you are all the better for the experience. I have done it and so have many others. Not all owners are so inclined. They have a problem with the car and want to fix it themselves as fast and as easily as possible. In fact, many have very little experience or knowledge or tools and are stretched to their limits just getting the old parts out and the new parts in. When you fix your old parts they may not be as reliable as the new parts you can buy and so may not last as long. A lot depends on your skill level. For the unskilled, replacement is the best advice unless they choose to improve their skills and have the time and tools to do the job. The consequences of saving a little money here can be an expensive repair in the transmission if you mess up and drive the car on a bad clutch.
David Teitelbaum