Serious Problem with 93 F-150

[mazingo]

Hello again,
It has been a while since I posted last and I have been having good luck out of my vehicles, mechanically anyway.
Well my truck (93 F150, 4.9L , 5 speed M5R2 tranny) has decided to put me down. I drove it home from work friday morning and when I got here I started to back up and it felt like I hit something behind the truck. Nothing there, so I thought I just stalled the engine. I started it up and pulled off no problem. The next day my stepdad got in the truck and tried to move it, but it acted like the rearend was locking up. I checked it out Saturday and there is a serious problem somewhere between the clutch and rear tires.
When I first bought the truck I thought the Throw out bearing was rattling but I later found out the the transmission was almost completely out of oil. I filled it up but I think the damage was done because I still heard some light rattling frome the tranny area. I haven't jacked it up and check it out, so it could be the rearend. But being that I don't know how long the previous owner ran it without trans. oil, I am betting on the tranny being bad.
I think one of the shaft bearings has slack in it, and the gears are binding. Has any one ever rebuilt a M5R2 at home or is it easier to just take it somewhere. I am pretty knowledgeable about automobiles but this will be a first. I have access to a press at work and I don't need the truck as a daily driver so I can take my time.

If any one knows a good place to by parts or a rebuilt unit, I'd appreciate the info. Thanks