Re: Oil pan will not come lose.
The OE gasket can be one heck of a pain to remove the pan on older 4.2s, 5.9s and 4.0s. Sometimes it helps to hammer in a thin blade, such as on old steak knife, every 3-4 inches or so along the pan rail to help loosen it up. Carefully lay the blade parallel to the pan rail and tap it into the gasket to cut it. Then give the pan a few whacks with a rubber mallot to loosen it. Be sure to straighten the pan rail before reusing it, or replace it with a new one.
If you don't have a new gasket yet, I'd recommend the new style silicone/ steel reinforced reusable factory gasket that is used on the newer 4.0s. Also, check for rust between the skid plate and the bottom of the old oil pan, one hit on a rock and you could cause a leak here. Hope this helps, good luck!