Details of the swap I made are in the '1872' page of my website. Rather than explain it all again in great detail I'll just send you there
There are lots of pictures and details there that will help you.
The plug is a one-time use only; drill/tap a hole in it and pull it out with a slide hammer. You can get new ones from CC.
The swap is much easier if you use the pinion shaft and ring gear from the CI rear. This is what I was intending to do but I couldn't because the ring gear in my CI donor rear was cracked. If you re-use the CI rear pinion shaft and swap ring gears onto the aluminum rear's carrier, all you have to do is take the pinion shaft out, swap the reduction gears, and put it back on. There are shims in there you may have to reconfigure, and you may have to file some casting flash out of the case, as the super reduction gear is thicker than the GT one. As long as you use the original pinion shaft that was in the rear, you don't have to screw with pinion depth adjustments and shims; all you have to do is get the carrier bearing preload correct before attaching the ring gear, and then moving shims from one side to the other until you get the correct contact pattern. If you put in a want ad for shims, you'll likely find some- that's what I had to do when I didn't have enough of a particular size.
I know it sounds scary but it's doable. Probably the worst part of the whole job is removing and reinstalling the Eaton retaining ring that holds the pinion shaft in. I think there's special tools for that but my dad and I improvised. If you want, PM me your phone number and a time when you'd be available to talk and I can give you a call and answer any questions you may have.