Dude99 is correct. The SLS shocks very rarely fail. They are also a rear chore to remove. If the rear of your wagon is bouncy more than likely the accumulators have failed; a simple check is to disconnect the fluid line from each accumulator and stick the eraser end of a pencil into the opening; if the eraser touches a soft resistance that means the diaphram in the accumulator is good; if the eraser pushes all the way through the diaphram has failed.

If your SLS system leaks down or will not rise, the usual suspect is the height control valve which can be rebuilt. They leak both internally and externally so even if you do not see an external leak, it may be leaking internally. All of this is based on the assumption that the SLS pump is working properly.