R12 to freeze 12 worth it?

i have a 93 plymouth sundance and the ac still works but not as cold as it used to be. its never been recharged either. so i was wondering if it would be worth it to vacuum out the r12 and replace it with freeze 12? have you had any experience with freeze 12?... i don't want to do a 134a conversion because id have to buy a new dryer and replace the mineral oil with pag oil which involves taking off the compressor... are there any danger to moving to freeze 12 from r12? i know most shops will vacuum out the r12 for cheap since its worth so much but should i do that or just top it off with a can of r12?