I have the same winch im looking at for a friend, ran into the same problem with the nuts! the winch is still on the quad so i have to take it completely off to get to the nuts lined up inside. Thanks for the video, it just confirmed what i thought i had to do!
Pull that end cap off of the drum and you can put them together on the bench, and then install the whole thing to the drum. Good time to add grease too
Those long bolts are bad to get out of line and walk in or out. Just have to keep wiggling them until they catch. The magnets are bad to pull them in one direction.