That was sort of a no-no. It takes 40oz of R-12 to refill; 32oz of r134a. Thats because you use less of the r134a. There's not a real simple answer due to what's inside of the system.
r12. If you decide to refill with the original refrigerant, it will give you the best A/C performance. You should also replace the accumulator which is the black canister just in front of the firewall with the 2 curved tubes coming out. The reason for this is its the device which retains any moisture from the outside air trapped and thus your system from becoming containated. Your lines were open, so it may not be effective anymore. If you don't do that, it might be just fine, but the risk of the compressor going out in the future is higher. You might as well go ahead and change all the Orings and add some oil while you're at it due to the cost of refilling. This would run about another $20. With 40oz @ $6/oz, you're looking at $240 + $50 + $20 + $50 (labor) which is around $360 or so.
r134a. If you instead do this, you will need to take extra care and flush each system part (Not the compressor! just drain it) including both of the lines, the condenser, and the evaporator. Replace all Orings with compatible ones, add 8oz of PAG or POE oil. You will need a new accumulator which is r134a compatible. Also you will need new fittings for the ports. Then once its put together, you can take it in for charging which will run about $80. So, for this its about $50 + $100 (flush work. less if you do it yourself), $20 and $80. So $250-$300. If you keep ths stock condenser, it won't cool as well. The condenser is the thing with the fins and tubes which sits in front of the radiator.
All of this assumes that you want the compressor to live more than 1 year. If you want to take a risk, it can be done for less. But if the comrpessor goes, you end up having to replace it, the condenser, and the liquid line plus do all the work again.
If it were me, Id probably stick with the r12, and a new accumulator. Even though its expensive, it will require less effort on your part and will work the best on your car. I retro'd my system for r134a, but I had to replace all of it except for the high pressure line anyways, so it made more sense.