XM211 Rear Axle help needed

Hi All,
Drained the oil in the rear diff.....Well, not quite...all that came out was a bucket full of water!!!
The diff appears to function, in that it is not frozen up, but at this point that is all I know.
This truck has been sitting for 10 years outside next to a building.
How difficult is it to open it up and inspect? Will I need any special
gaskets to re assemble or can I make my own, and out of what kind of gasket material?
Is it likely that I can just clean this puppy up and refill with oil, or am I going to have
to replace gears, etc, or the whole axle. I know you can't give me an accurate
answer, but a good guess based on experience would work fine.
Any other tips etc. would be very much appreciated.
Thanks,

i would pull the hubs and the rear to get to the bearings, if it sat that long the bearings will have started to pit, thay will have to be replaced if so, the gears most likely will clean up unless they are pitted below the hard face , then thay still may be saveable

I'd be afraid of rusty bearings/gears, but maybe operating it unloaded (on jack stands) with some gear oil will clean it up, worked for a ford rear end and i never had any trouble, but that's not the same at all! Taking it apart is the right thing to do, but what a job!