The cam can be done with proper research and a good understanding of how an internal combustion engine works. It's really not too bad with the right tools and mindset.
The gears on the other hand, you really need to let a pro do that. I am considering attempting to regear my car back numerically lower some, but I haven't seen the process involved yet either. I also have access to a lift and several tools, then I am a machinist by trade so measuring instruments are not an issue.