What would be helpful is to start soaking the barrel/pin/frame "affected area" asap in your bestest nut buster oil. That'd give the buyer a head start on removal of the "offending member". Lotsa info on the interwebs re barrel swaps on Masks; and most makes are fairly comparable. Like Frank sez; proper tools are pretty handy. Or just send it off to some alley in Afghanistan...those guys can make any type of gun parts out of old hummus cans and leftover Invader Eqpt.Like I said, other than the barrel being bulged, everything else seems OK.
They might even have an old ruski armorer's chest in uncle Mustafa's barn.