OK, I'm new to this board but I'm MACS Cerified and can straighten you out on a couple things.

Yes, that stuff on ebay is R12 refrigerant with an oz. or two of oil in the can. Buy it, get a can tap and top off your system.

No, that Freeze12 crap is not R12!! God knows what it is, but probably R22 or R134.

No, R134 isn't as good as R12 if you ask me, but it's just my opinion.

No, retrofitting an R12 system to R134 doesn't cost $1000. Recover what R12 is left, change the reciever/drier, maybe drain the old oil from the compressor if it's easy to get to, add a few oz. of PAG oil and some UV dye, change the charge ports, vacume for a good long time and re-charge. You'll take about 15% less R134 in the system but it should work ok and be cheaper to fix when the next problem occurs.

jim