Ah well thats a mouth full. You can chop up the guns as long as the parts compliance is correct (922r) when you are done. You can tap and screw the front trunnion if you like, riveting is better.
Part 2 you could do that, or you could mod the bolt and carrier for blow back operation.
Im sure others will be along this morning with more info. Also you might want to do a search on 762x25 rifles as there are several excellent posts on these.