Kits are good for learning about circuit assembly, they are not the best thing to learn how the circuits work, at least in my opinion. Most kits don't include any theory of operation. But circuits are circuits, and all amps pretty much work the same way, so circuit explanations for one amp often apply to other amps. Oh within limits of course.
Just hop in and start doing stuff. There is tutorial material available to learn about circuits, and kit building or repairing existi9ng stuff helps learn about how things are made and helps learn to identify components.