Andrew,
Your coach does have a desiccant bag. It is located inside the dryer that is probably located on your front cross member, but you should just add a little i34A refrigerant to your system to start with to evaluate its cooling capacity before replacing any parts. Desiccant bag failures are not common, but most of these teenage coaches have very small leaks in the dash A/C, so it is fairly common to have a coach that just needs a can or two of refrigerant added every year to keep it cooling to your expectations. If your coach has not had the dash A/C serviced for several years, you may need 3 or 4 of the 12oz. cans to git it cooling properly.
After you get the dash A/C cooling, if you only need to add one or two 12oz. cans a year to keep it operating properly, there is nothing else that needs to be done to the system. Trying to fix all of the leaks on a 15 year old dash A/C system could easily run in excess of a $1000. So just adding $10 of 134A a year is a much better choice.
Your charging ports will be located in one of three places. Either at the compressor, under the front cap, or inline just before the refrigerant hoses leave the engine compartment. First look at the compressor if you have a side radiator, then under the front of the coach, then if no success yet try the hoses as they leave the engine compartment (mostly on rear radiator coaches).
Gerald
