Very easy to do. Remove 2 bolts from idler arm (passanger side of car). This will allow you to pull down on steering system enough to remove oil pan. On your 81, the exhaust may be in the way, but I'm not sure. Are you replacing the rear main seal? If not, I would while your in there. When you reinstall, go with a one piece oil pan gasket with little plastic guide screws. These screws thread into the 4 corners of block and allows oil pan gasket and pan itself to rest on the guides while installing. Also lines everything up. Makes life so much easier. And the gasket is reusable. It cost more but is well worth it. Check your local autoparts stores or order from Summit.
Job for the weekend. I have a new timing cover to go on as well and the exhaust is already off ready to fit sidepipes. I have a Felpro gasket set so that will have to do for now although I intend to use studs instead off bolts so it should go back together a bit easier.