Rear Main Street Seal?

[Apache809]

This is a project truck and been work on it little by little. I started with the electrical system. I finally finished all the wiring stuff like headlights, tail lights and such. I turn it on once in a blue and drive it around the block.
Last week I started noticing a little oil on the ground. It wasn't much to have me concerned but today since I finally got tail lights, I decided to take it for a longer spin. I drove it about 5 miles to advanced auto to pickup a few things. The drive was ok but the last gear felt like it needed one more gear to go smooth. We made it to the store driving at about 40 mph because any faster and I felt like it was being overworked.
When I came out of the store I noticed a puddle of oil about 8 inches wide on the grownd. I looked under and saw oil dripping but from between the engine and tranny. I asked one of the vulture mechanics that hang around the store and he very quickly determined that it was a bad rear main seal. I put a quart of oil in it and drove it home. But on the drive home I forgot to disengage the parking brake. I only knoticed because of the smoke coming from the floor. Disengaged and the smoke stopped. Once home I didn't have parking brake. Yea, double whammy.

How hard is it to replace the seal?
Im a do it yourself type of guy and might have all the tools, but is this a job I can do on my driveway with a buddy?