Yes, 03 was the first year of a new chassis. Only major carryover components were the transmissions, and the diesel, but it was significantly changed too.
Similar front suspension design, but different axle in the 4wds. Dana in the 2nd Gen AAM in the 3rd gen.
Not the cause of problems with your truck per se, but the 3rd gens were supposed to be stouter.
Both had/have weak steering box mounts and questionable steering box quality. I have a brace on my 07 steering box, not because it steered bad, but because I saw one that parted ways with the truck frame. Not a great design but the brace is a good fix.