HA!! You may get out of it for 30/40 bucks! FIRST thing to check is the u-joints... You describe a bad u-joint pretty well.
If they are both really tight and good then the NEXT thing is pinion bearings.. I really doubt the R&P went away.
Have you even checked for water in your rearend?
Seems you are going off half cocked..to me anyway. You MUST know what is making the noise before you will have any idea how much it will cost..
Put it up on stands and start her and let it idle while you crawl around listening.. You MUST find the noise before tearing into it.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />