Been doing this awhile, and have learned over the years that there are things to mess with yourself, and things not to. The rear shock has a couple issues from the factory, that the suspension shops will fix if you send them the shock. The piston is not tight tolerance between the inner shock body and the pistons, which allows oil to travel around it undamped. The seal for the shock rod is on the large side, so can start to seep or leak prematurely. There isn't enough oil in the shock from the factory, and the bleeding process is tough to do without the proper equipment. Yes, you can get the parts, but without the skill set to install them properly you're not getting the most out of it. The valving is lousy from the factory for aggressive riding.
Just getting the rear shock to work makes a big difference. If you can afford to do only one end, that's the end to do. The forks can be tuned around a bit to at least make them work okay for you even without a spring change. Springs for your weight/riding style along with better valving and low friction seals make them work pretty darned well in my opinion. If you want to learn about shim stacks, valving and oil weights on your own, the front shocks are the place to learn because they aren't under 200 psi of nitrogen pressure.