Holy **** people, shut your yaps if you think a new transmission is the fix.
It's almost certainly an input shaft bearing. If you have access to a press and have a decent skill set, it's not at all difficult to do. Time consuming yes, but not hard (or expensive)
You'll need to replace the bearings (red) and replace the front seal while you're at it. You also need to replace the center diff to transmission gasket while you're in there.
Reference this thread on how to fix it
http://www.rs25.com/forums/f105/t128...lkthrough.html
And this one for how to get the tranny apart.
http://www.ultimatesubaru.org/forum/...l-replacement/
You can reference this image out of the FSM for what parts you need. 1 is the front seal, 2 is the little needle bearing, and 14 is the big ol mammjamma that makes all of that noise. I forget the other numbers, but 14 (The big one) is 806225100