What is wrong with my truck?

[TexasPride]

I am traveling home from Christmas vacation with my wife. About 10 minutes after getting gas, the engine starts struggling and lurching as though it were running out of fuel. Stepping on the gas didn't do anything. I steered it to the side of the interstate and called a tow truck. I tried to restart the engine several times while waiting, but no luck. They took us to Pep Boys, who were useless. I had them drain the tank and replace the fuel filter, figuring it might just be water in the tank from a bad batch of gas. I did look at the gas and it did not look cloudy or show separation. The mechanic said there was some water in my exhaust, but didn't know how it got there or whether it was the cause. The annoying part was that the truck cranked and ran fine for them. They said nothing was wrong and sent me on my way. 5 miles down the road, the engine crapped out again. A nice person helped me push it into a truck stop, but by then it was after 7:30 pm and everything is closed. We are spending the night sleeping in the truck with no idea what is wrong with it. It's a 2000 GMC Sierra 1500 and it has run like a champ until today. Any ideas what could be causing this?