Building systems takes a long time because they would have to do all sorts of checks and tests to make sure everything works. There is also the problem of compatibility. You might through mistake or ignorance go for a C2D and then choose a incompatible mobo. Means more messing about.
Basically do it yourself you lazy git
My first full self-build only took about an hour including breaks for tea
Overclocking is also quite easy and most of it is waiting for stress testing to pass or fail. Also, you can take a break from your overclocking whenever you want. If you keep a detailed list of all your settings you can easily pick up where you left off.
SiriusB
Basically do it yourself you lazy git

My first full self-build only took about an hour including breaks for tea

SiriusB