I need some to get my compresser running so my damned windows wont fog up when I turn the heat on

 

You can't get freon anymore over the counter. I believe the only way you can get it now is if you have at least a spec. 6 (automotive) A/C certification. If you need to get the compressor running, there's a low pressure switch that will shut the compressor down if the freon load is to low. This prevents the compressor from cycling and buring itself up. However, it is an extremely bad idea to run the compressor without the gas, for this same reason.

 

I can't just take it to Grease Monkey or something and have them dump it on in?

 

What year is your truck?
Does it use R-12 or the newer stuff?

 

The R-12 needs to be done by a facility. WalMart has a conversion kit for about $30 but I do not know if you will need additional cans of charge for the complete system. By '92 need to have the R-12 charge and rumor has it that runs $100. There is a place by I-25 and DTC that came recommended for the job but I can't recall the name now...
--Mike G