The cost for the Valve cover gaskets included the labor involved - price may not be 100% accurate, as I had a few other maintenance items performed at the same time.

If you're doing the job yourself, labor cost is not a factor for you.

The '91 Rodeo that I had, had a whole different engine then the '91 Trooper you have. I never had to replace valve cover gaskets or headgasket on the 3.1L GM engine.

I have no knowledge of the 2.6L engine and the issue concerning the heads.