Originally Posted by 68 TWind
If your inside lights are the square ones with 4 bulbs and a 4 position switch, unscrew the on/off switch knob and there is a retaining ring under it that you unscrew and the plastic cover comes off. Since aluminum doesn't rust, the rust must be coming from the steel top of the step. I like scotchbrite pads to clean up aluminum where the finish isn't going to be polished. Don't' use steel wool on aluminum.
I had the same questions with the door gasket. Raining here now so I'll look tomorrow and see how I installed mine but I am pretty sure I put it along the bottom. Send me a PM if you would like pics of how my door gasket is installed.
GREAT tip on scotchbrite versus steel wool.
For the light, see if you can press a REALLY skinny/small screwdriver blade against the shaft to keep it from slipping, while you turn the knob to loosen. Seems like I had the same problem with a bad switch. Once that comes off the light cover can be removed by loosening the retaining nut. When you take off the cover, you'll see the screws (I think there are four) holding the entire assembly to the ceiling. You may have to remove the bulbs themselves to see all of the screws. Keep us posted... dig the pics.