CEL = check engine light, sorry didn't mean to confuse you on that one.
If you don't know how to get the code out of the truck, it is pretty easy. You just need to find the little port under the hood, can't remember which side it is on, but it is about 1" x 2" with a grey cover that says Diagnose on top of it. Use a short length of wire to jump tow of the terminals, I can't remember which ones off the top of my head. With the jumper in, you turn the ignition on and count how many times the light blinks. The number of blinks is the code.
I don't know that it is the HG. Have you changed the fuel filter, ever? I would try to get the code first before you go all in on the HG. The TPS could cause the symptoms that you are describing as well as a clogged fuel filter. The fact that it is stumbling on acceleration sounds more like a fuel starvation problem, especially since it seems to do ok when you gas it slowly.
TPS is pretty easy to change, I think it is on the backside of the TB and held on with two bolts, and the fuel filter on the V6 if i remember is actually on the passenger side frame rail, so pretty easy to swap also.
Check those before you go after the HG. If you had the recall done and you haven't overheated it then I would be surprised if it was the HG.