I have that same winch and thats a fair price if it's in good condition.
A few observations:
If the neutral lever is stiff or inoperative it means water and/or mud have entered the planetary side of the winch. Once water gets in it can't get out so all the steel components start to rust. This can be serviced and fixed easily if you catch it quick enough.
Same story if the winch doesn't freewheel smooth and easily. Easy to fix if you service it soon.
The missing bracket is simple to fabricate if you have even moderate skills. A 6"x4" piece of 1/8" mild steel is all you need. Shape it, bend it, and drill it. You have yourself a bracket. Depending on how long your wires are you might be better off mounting the control box remotely and out of the elements.
These winches need a good ground wire. #2 cable or larger as short as possible to get back to the frame. Then make sure you add an additional ground wire from the battery to the chassis under the hood. Lots of people use a nice big power cable but neglect the ground. The ground is just as important.
If you do get this winch the first thing you should do is take apart the planetary side and clean it up. The drum on this winch is not sealed and water/mud/sand/grit gets in easily. The planetary side is simple to disassemble and service and it will make the winch perform as good as new. I soak all my planetary parts in clean used oil before reassembly. They work much better with a little lubrication. The planetary side is simple and it's impossible to put it back together incorrectly. If it's not correct it won't go together. Look at the link below for a complete parts list and an exploded view of the inside of the winch.