I have done it repeatedly, but just for general maintenance or to eliminate the coil as a suspect when I had a problem. Mine were not seriously corroded when I got them apart. From memory:

Remove ignition wire to dizzy and input wires from the bottom. Two 10mm bolts allow removing the coil from the car. Coil is held together by torx hedead screws (#25?), two of them, I think, in the corners. Once the box is apart there is an abvious strip of metal which contact the other side. I used fine sandpaper to clean this contact strip, and the other side where it contacts. Not being sure if it mattered but sure it couldn't hurt, I also cleaned up the contact points between the two halves of the box and where the box bolts to the car on the chance that it needs a good ground through that route. Reasembly is the reverse.

I did not use any electircal grease and I am always a little confused which kind to use when anyway. I think dielectric grease is an insulator and so is used when you have something like where the wiring harness connects at the bottom of the coil. There, you want to protect the contacts from the elements, but you do NOT want current to pass directly in between the wires through the grease. The other case is like where the coil to dizzy wire connects. There, you only have one wire, so you want a grease that will not only protect, but also conduct electricity and so give you an even more certain connection. I'm sure someone wiser than me can straighten me out on what the two kinds of grease are called.
--
Andy in St. Paul - '91 745 227K mi, '91 745 210K, '90 744 194K, all Rex-Regina; '86 745 GLE M46 230K; past 240s