before you do anything, make sure it is actually the intake manifold. With the Jeep running, spray carb cleaner around the intake ports at the head. If the idle changes, then yes it is leaking. You can also try re-torquing the intake manifold bolts and see if the help. Heating and cooling over time will cause those bolts to loosen. You may be able to re-torque and fix the problem.
Most important thing here is torque them CORRECTLY. That means the proper amount of torque and in the proper sequence. You should find these two things through a google search. Further, I would loosen all the bolts first, and then torque.
Worst case scenario, you have to unbolt the intake, slide it away from the head, scrape away the old gasket, fine grit sand paper to clean the two mating surfaces, then slide in the new gasket and reinstall. If you go this route, buy a Felpro gasket and get new intake manifold bolts.