[Russell]

Not that bad... If you have a two piece seal, you just need to undo the engine mount bolts, and jack it up high enough to get the oil pan off. You then remove the rear main cap, use the seal from the bottom half to push the top half out, then stick some oil on the new one to lube it up, slide it in, making sure you center it, then lube up the bottom one, put it into the main cap, torque the maincap back down, put a single peice silicone pan gasket onto the oilpan, torque it down, drop the engine back down, then change your filter, put new oil in, and go.

However, that said, if your truck has been sitting for a while, drive it for a few days and see if the leak goes away. Old seals dry up, and start leaking, but seal up once they've soaked in oil for a while.