Checking Your Shocks
The best way to check your shocks is to hold them adjuster downwards and push and pull them through the full length of their travel a couple of dozen times each. If there is even resistance with no "free" spots, your shocks are probably good for a bit more use.
You probably already know the springs can be removed and re-installed by putting the shock mounting bolt through the eye with the springs in place (and the shrouds if you are using them) and using the handles of a set of pliers to hook under the bolt while you push down on top of the spring or upper shroud so you can remove and re-install the retainers.
Obviously, first the adjuster must be in the lowest tension position or it is hard to do, and the lower eye should be clamped in a bench vice or bolted to the bike.