I completely agree with 6880 Mike. I just finished (sunday) my 134a conversion, and its a good deal of work to do it right. If your getting cold air now, dont mess with it. As they say, dont kick a sleeping dog. Once it quits or stops blowing cold, then convert. If you just have to do it now:
You dont need the Ecklers kit!!!!!! Just get a reciever/Dryer for $55 bucks, an orifice tube for $3 bucks, a set of O rings, a can of Ester oil, 4 of the little cans of R134a without oil, an orifice tube removal tool, the correct fittings for the Shrader valves, a can tap, a set of manifold gauges with hoses, and a vacuum pump.
Evacuate the system, replace the Reciever/dryer and the O rings for the fittings(pour 3 oz of ester oil directly in the Dryer before installing), and replace the orifice tube and its fitting O ring. Remove the compressor and drain the mineral oil. Pour 3 oz. of Ester directly in it, then re-instsall it and its O rings. Install the proper connections on the schrader valves, usually from a retro kit at any auto parts store. BUT, you will need a 90 degree for the low side, (ill send a link for it if you do this). Then vacuum the system for 30 minutes, and fill with 51 oz. of R134a. This is 85% of the amount the system calls for R12. 4 of the little cans of R134a is 52 oz., (they are 13 oz. each) so that is what I used. And then your good to go.