If you heard a hissing noise and the AC suddenly quit, I'd say knowing the high side from the low side won't do you much good now. (FWIW In the case of my '96 Dakota, the low side connection, which is the ONLY side to mess with, is on a line that runs along the passenger side fender. There's a little plastic cap on the fitting.)
It sounds like you had a loss of pressure due to a major failure, if the hissing you heard was escaping refrigerant. Time to take it to the shop, just to eliminate that possibility.
BTW, after running the AC for a while, mine always hisses a bit right after I turn off the truck. I think that's normal, as it hasn't had any rapid leak-down. If that was the source of your noise, and the AC coincidentally stopped working due to a PARTIAL loss of pressure, then you might be able to just charge it again. But I would take it to the shop first, anyway. It's usually less than a hundred bucks to have it tested and charged--and if you lose the charge again right away, they should credit you at least the cost of the refrigerant when you take it back.
Refrigerant lost due to major leaks and component breakage in accidents was a major reason that they switched to R134a in the first place. That's what dumps a whole load of refrigerant into the atmosphere at once.
One more note: Freon is a trade name for R12. Technically R134a is not Freon, but "refrigerant." R12 is also a refrigerant, but sometimes known as "Freon."
Probly more than anyone wanted to know...