We went from a Chevy 3500 duly gas (used), to a Chevy 3500 duly (diesel), to a Chevy 3500 duly (diesel) - Duramax.
We traded the first truck because the frame was rusting so bad, but what a great engine! Our dealer-service shop pointed that out to us. The first diesel had a fiberglass body, but what a great engine and transmission. We were concerned all the spider cracks on the fat fenders would eventually make the entire side of the truck fall off. It was all one part, and to replace was $4000 a side. We traded while it still looked salvageable. Third and current truck, bought brand new! OMG, the other two don't even compare! Integrated brake controller, Duramax Diesel, power... power ... power! No regrets at all.
However! The one additional thing that took a bit of getting use to with the last truck is the necessity for DEF fluid. It took a learning curve, still wish it wasn't necessary, but too late now. That's the only regret! I always keep an extra jug of DEF fluid now. Never had to do that before.