It�s been more than two decades since I�ve disassembled a milled AK, so I don�t remember if it has the bent paper-clip pin retainer that the stamped rifles do. If it does, getting it back in is a straight up pain in the arse. Other than that, the replacement of FCG parts in an AK are as simple as all get out. There�s a gadget that replaces the paper-clip spring called a Shepherd's Crook, available here:
http://powercustom.com/store/index.php?main_page=product_info&cPath=15&products_id=166 If you work up a little Google-Fu, I�m sure you can find both photo and video instructions on how to do the whole thing yourself. Good luck my friend.
