To Sell the last of the R12 or let it fade awaaay?/

Whats your question? R-12 is DIY dead. You can still buy it in Tijuana, just fill it there..DO NOT try and bring it back, even with a license. R-134 is still legal to fill yourself, changeover is minimal. BTW, Duster cans are pretty much R-134 too so whenever you dust your PC or blow your air-horn, you are venting.