While not for a Jeep, this might give you some good ideas on what needs to be done:
http://www.mkiv.com/techarticles/headlights/index.html
In the Supra world where I usually spend too much time, polishing the old yellowed and dulled plastic headlight covers is a common and well developed technique to make them clear again. I saved my original plastic ones in case some day I have nothing better to do I'll try to polish them, but I haven't tried it yet since I just bought the glass covers that were sold on European Supras and they are as clear as ...glass.