sm420 is just like any standard xmission, not a big deal. The one thing thats gonna puzzle you though is when you pull the input shaft, all the little pocket needle bearings will fall out. thats normal. to put it back together if i remember right there are 14 of them? just pack them in the hole with grease and it will go right in... The Input shaft also has a cut on the bottom of it that has to line up just right and cocked a tad to get it out over the countershaft. Otherwise just a transmission, none of the bearings are even pressed that hard...can rebuild it with just standard tools and a small persuader... hehehe.
