Summit Racing also sells some Warn parts, FWIW. You can get the Warn suggested grease, Aeroshell 33MS (or 64) from Amazon. A tube of it will cover you twice over.
I have the regular XD9000 where the control pack isn't integrated but is otherwise similar. I've rebuilt it a couple of times. With a little bit of searching you can find the parts diagrams and rebuild manuals for step-by-step procedures. Knowing serial number will help because there's a few generations of the XD9000. Although parts can interchange to large extent even between M8000, XD9000, etc. I believe ranges of SN can dial in the right part number with respect to the motor, clutch and such.
Mostly as long as it's functioning you're looking at a lot of cleaning and then a handful of gaskets, o-rings and a few small parts like detent for the clutch handle, a couple of drum support bushings. You might consider the long hex shaft just on principle since that's most likely to twist or break when stressed.
If you're even slightly mechanical it's not difficult with the only tricky part is if you decide to pull out the brake to rebuild it be methodical and follow steps to the letter.
I would suggest stripping it down completely and having the drum media blasted. Between maybe having steel wire rope and the rust I'd want it smooth and clean. By media I would be thinking bead or walnut shells, something that will really smooth it, more than sandblasting alone. More like de-burring instead of just stripping the paint and rust. A decent machine shop or powder coater would I think understand.
Edit to add: You might also need motor brushes, although I don't know if that's a Warn standard part or aftermarket on eBay or similar.
Also attached a bunch of PDF service documents for the XD9000 that I had squirreled away. If you have the serial number I also have a few parts lists PDFs stashed and would be happy to post the applicable one.
