I have a 239, but I've honestly never thought about disassembling it to that extent. You may have better luck posting your question here: www.sigforum.com
If I remember correctly, you have to drive the cross pin out and if I remember that correctly, it comes out from right to left. For reassembly, be sure that you get the firing pin right side up so the cross pin will match up with the channel. Keep yer powder dry, Mac.