Last summer I had to clean out my black valve, dummy mistake, repeatly opening and closing valve during winterizeing I jammed TP in the valve.
The hardest part or tidious part was the underbelly.
Mind you the valves are in very tight between the pipe. You will need something to separate the pipe, just enough so you can easily remove the valve but mostly so you can properly reinsert the valve with the o'ring still attached.
Ah once you do one the other 2 will be easy(ier).
Not exactly sure on what you meant really. Are they stiff if so maybe try grease the rods on the handle, unless you have cables which I hear can give you problems.
Or are they leaking, if so you can spin the handles which will push the gate to seal properly. Just make sure you don't loosen the rod completely.
This is what I would try first, as for the electric can't help there.
07- Classic 2500 LT CC 4x4 SB Duramax/Ally
13-320RLT Crusader TE
Reese 16K Kwik Slide/Prodigy brake contoller