I assume you mean the fluid leaked out of the compressor? To properly diagnose the system, it needs to be evacuated with an A/C machine, then filled with refrigerant and have dye injected into the system. Then the A/C system should be run, and using a UV light, watchfor a leak. The dye will glow as it leaks from it's leaking part. Sometimes the leak is large enough the UV light isn't needed. This type of work is best left to a shop with the proper equipment to recover the refrigerant. Most places run specials for $40-$70 for this type of work. If they diagnose it and want too much to repair, just have them recover any refrigerant, repair the system yourself, and then go back to them to have a vacuum pulled on the system to make sure any contaminants get removed, and then have them charge up the system and then enjoy your cool cab. It sounds like a lot, but it's pretty routine for any shop.