Good luck. Too bad it wasn't a half a year newer. In '01.5 they got rid of the CAD. You won't have any problem with it. My Dodge is actually an '01 as well. I've had the front end of my truck bouncing off the ground on more than one occasion with the 1200lb Cummins in the front pulling 25k rigs out of the sand at the dunes. Like you said it may be a unit bearing, but it's a huge beefy unit bearing.
At first I thought I was doing you a favor selling you a rear axle with 5 on 4.5. Sorry you have to convert it to 8 lug anyway.