If it's in the same location as my 04. It is near the firewall on the passenger's side, both the high and the low. No special refrigerant required just your auto parts store R134 should do it.

 

If you are low or have lost all your refrigerant you have a leak..fix that first.

 

Could have but not neccessarily....
A/C systems charge can evaporate over the years, recommended top up evry 5 years or so.

 

Some parts stores sell recharge Kits and cans of 134a. most people believe that the A/C unit in a car naturally loses charge over time. Big myth.. an A/C unit is sealed, nothing can get in or out without there being a leak. Before you waste time recharging it yourself, find the leak, either a loose fitting or a bad O-ring in one of the snap fittings, or even the compressor shaft seal, I highly recommend taking it to a A/C technician so that it can be properly inspected, repaired and evacuated to remove any moisture or other contaminants that may be in the system, in the event that your charge is flat..

 

Nothing wrong with picking up a quick recharge can to put the cool back in your cat. However Colt is right, freon went somewhere and the only way to find out would be to take it to a A/C tech and have him sniff it out with a freon sniffer and look for traces of oil and debris near the fittings and the drier.

 

The gas naturally disappears through any rubber part of the system over time eg seals,some pipes etc
Just speaking to the guy from the a/c company who has to discharge and regas cars at our bodyshop now (Health and Safety) and he reckons the a/c system can loose 10-15% each year so after 5 years sometimes little left.
He recommends getting the gas level checked every 1-2 years.
So to me that dismisses the myth theory ie you may have no leak it could be just natural wastage