95 A6 Driveshaft rattle

[beattyr2003 at cox.net]

1995 A6 with 260k miles.

Getting a rattle from under the car and after a bunch of poking around, finally figured out that there is play in the main driveshaft where it attaches to the rear diff.  When rotating the driveshaft it will rotate a bit before the rear diff starts to move.  So I am thinking the rear U-joint (or CV joint?) is bad and needs to be replaced.  When I was under the car, I didn't get the impression the rear was removable from the driveshaft, but there are repair kits out there.  So does that mean you disconnect the shaft from the diff and replace that section of the joint?

Anyone got any BTDT on this?

Thanks,

Rob