You need the clutch packs? This is where I got the packs for my Power-loc. I have a D60 and a D44. They might be able to hook you up with the AMC20. Or Randy's ring and pinion can help ya.
As far as taking them apart, that is pretty simple. Pull the center pin and rotate the spiders to the openings. Pay attention to the order everything comes apart so you can put it back together. Make sure to soak the new packs before installing.