Taking apart a winch is pretty easy. You can find exploded views online (I recall that MontanaJacks had some good ones).Tool-wise, all you need is an allen wrench set (standard).
First use a multimeter to test power to the winch--you may have a defective relay or blown inline fuse somewhere, and not a mechanical problem with the winch.
Most common problems with winches are stripped gears (pretty obvious when you disassemble the winch), bad electrical connections, or improper lubrication. You can get parts from either a Warn repair center (there's one in Anchorage on 4th Ave.), or probably your Polaris dealer. The specific grease Warn suggests is virtually impossible to find, so I used green Aeroshell.
If you have a digital camera, I'd highly recommend taking pictures at each step, so that you can get it all back together on the first attempt. There are not a lot of pieces inside--just a few gear assemblies (which remain together), a rod, and a spring.
Note which color wires correspond to which terminals on the winch, and remove (take a picture/make a drawing first)
Note how the winch (or mounting plate) is installed to your ATV (again, drawing or picture)
Remove the winch (possibly still mounted to the plate) from the ATV.
If you haven't already, remove the winch from the mounting plate, noting the orientation of both the winch and the plate. (Dwg or pic)
Note the direction the winch cable/rope is spooled, and where on the winch is passes out (there are two "bars" on the sides away from the mounting plate--note between which two points the cable passes). (Dwg or pic)
Remove the allen screws holding the two sides of the winch together (at either end of the " bars", and separate the winch ends from the drum.
Note the orientation of the center rod (which end corresponds with the motor versus the clutch), and which end had the spring. (Dwg or pic)
Then there are flat crescent-shaped pieces which holds the internal gears inside the motor bell or clutch end. Remove these.
Remove the gear assemblies (typically a round disc with a center gear and three planetary gears on the outside), noting the orientation and order. (Dwgs or pics here).
Clean everything off and inspect. On older winches, pay particular attention to the inside of the clutch end, as the gearing in here can be plastic, and is prone to stripping. Once satisfied that they are all good, grease the snot out of everything!
Reassemble in reverse order of disassembly, making sure that the drum fits snuggly between the two ends, and that the cable is exiting at the right point on the winch.
You should be able to find the parts and the breakdown of your winch here.