...Once you have removed the Superwinch hubs (or hub covers for those of you who do not have manual hubs), take a rag and wipe away any grease that you see on the end of the axle shaft...

...Install the gaskets for the "hub/bearing cover/hub flange" (I used RTV silicone/gasket maker). Reinstall the "hub/bearing cover/hub flange"...
My interpretation is that the Superwinch hubs as well as the stock hub covers are sealed with a gasket. Apparently he couldn't find the part either because he used RTV instead.

Let us know how this job works out for you and any tips you have. I need to do mine very soon also!