This is an age old problem since refrigeration began; you will need a Pro to fix your beer fridge and that's only if you can find one that likes your preferred brand to make it somewhat inexpensive... Personally I like Miller Lite and have my own kegorator neatly handy... You have made the ultimate sin in the refrig world of using a sharp instrument to remove ice from an evaporator coil.. Next time use a hair dryer or just unplug the unit for a few hours with door open.. As for R12, there are replacement refrigerants available to a Pro that are compatible and cheaper... You have to be EPA certified to obtain these compatible refrigerants... The mineral oil used with R12 will not work with the newer 134a refrigerant... Hope this helps, kooler

Wow, didn't expect a lengthy response but still glad to offer info... Without getting too involved with Refrigeration 101 I'll try to explain some vital details.. Refrigerants are very touchy chemicals that like to work alone with the exception of compressor oils.. Try to think of the tubing inside your beer fridge as off limits to any outsiders, it needs to be almost exactly like outer space, outside of earth's atmospheric environment.. I say almost only because one would have to journey to outer space to acquire that environment.. But man can come close with the wonderful invention of a vacuum pump.. A necessary tool usually only owned by a Pro refer dude (or gal) because of the expense... The fridge compressor itself or a reclaim device can act as a vacuum pump but will never attain the needed deep vacuum to bring a fridge system down to where it needs to be oust undesirables and to obtain the optimum enviroment before 'injecting' R12 or any other refrigerant... We use the term 'charge' when referring to injecting refrigerant.. And you, my lager-imbibing friend, have made another 'dumb' move by running your fridge even after poking a hole in the evaporator coil... With the release of the 'so-called' ozone depleting refrigerant your fridge cooling system is now empty and the evaporator was subjected to a 'vacuum' which in turn would draw or 'suck' in air and moisture without a doubt thru the newly inflicted 3mm hole with a saran-wrapped screw secured in place... BIGTIME no-nos; your system is now contaminated with air and moisture.. You emptied the system with the first arterial bleed, no more R-12, not even a residual amount... This is something that can happen with a hole that's 50 times thinner than a human hair..
That's why you need a Pro to come visit or better yet, take the fridge to him and work with ice chests for awhile or your PA back porch during JAN... That wouldn't work where I'm at, it's -20° while I'm typing this..
Now you can attempt to repair this hole with aluminum rods like you see the guy at the State Fair who welds several beer cans on top of one another but you still face the problem of a contaminated system so either look for a replacement fridge or take it to a Pro and remember to be kinder and gentler to your trusty and often-taken-for-granted cooling friend... And please pass on your newly gained knowledge to your comrades with libations in hand...
Cheers, Kooler

I agree, the costs associated to repair this machine will be much more than buying a new or used one. Check out Craigslist in your area as they always have people selling good, used beer fridges!