Fairly straightforward repair. Remove the 2 scews holding the door to the hinges and remove the door. Then, remove several layers of screws to get to the seal. There are a lot of them, but they are obviuos. Replace seal and reverse process.
Be carfeful removing the screws. Because of age, several of them were frozen. I stripped the head on one of them, and eventually had to use a drill and screw extractor (which worked fine). You might want to get some 8x1/2 sheet metal screws before you start. I replaced all of the old srews on the innermost panel with new ones.
I used a tip from the comments here. Replacing the door on the hinges is difficult because the hinges are spring loaded. To make it easy, wedge small blocks of wood in the hinges to hold them open. The door then slides on the hinges easily.