Truck hauling question
 

I have a 2002 Chevy 2500hd. I'm trying to go from Seattle to Dallas with at 3k pound truck camper and hauling a 3k vehicle on a flat bed. Can this work or am I going to tear my truck up?

Without knowing which 2002 2500HD you have this will be a general answer.
Your towing capacity is 12000lbs while the payload is approx 3,177 to 4,074 lbs

It is a duramax Diesel V8. Can I do both at the same time? Is there weight on the hitch from the trailer that might mess with the payload?

Yes the trailer tongue weight would be calculated into your trucks total payload

You need to find the GVWR and GVWR of the trailer. Here is a very informative link that might help you Travel Trailer Weight Calculator

You'll be fine lol.... I don't think you can kill a duramax