I have the 2500 AV, 2002, and I love it. I have only towed 7000lbs, but I can tell you it does it very well. Others tow lots more with their 2500 AVs and Suburbans (same exact running gear). I have also upgraded with wheels, tires, K&N FIPK, true dual fllowmaster exhaust in all polished SS, airbags, and a host of other goodies.
Is your dually in bad shape? Or is it just outdated? I have to admit, if you already have a diesel dually, that has no issues, I would keep it until you are done with it. I bet it is paid for, and being a diesel, you are going to get much better mileage with it than the 8.1L. I get about 11-13 daily driving, and towing is less than 9. Honest, keep the diesel dually for a while.