[Geerhed]

It is very easy to add coolant, but you have to pay attention so you don't over-pressurize the low pressure side of the AC system (you have to open the valve slowly and 'regulate' it to keep the pressure needle on the fill-kit in the 'green').
Wal*Mart (and others) sells a R134A re-fill kit (8 - 12oz bottle of refrigerant, plus a fill tube with a pressure gauge and the proper fitting for the low pressure side (it won't fit on the high pressure side so you don't have to worry about hooking up to the wrong fitting).
Cost you about 10 bucks. Another 4 - 6 if you need a second bottle of R134A. Follow the instructions on the kit.

If I've given bad info, I hope someone will correct me, but I've been recharging my own AC system for years and haven't screwed anything up (yet).

Good luck!

 

[Geerhed]

Burnside:
The Low pressure side on your van is the fitting up next to the firewall (beside the computer mounted on the passenger side of the firewall).

 

[Geerhed]

You need to have the vehicle running with A/C on Max AC and fan on full when you're adding the coolant.
Make sure you shake up the can until your arm aches. :lol:

The fill kit will NOT fit on the high pressure side. However, it does take a little while (10 minutes or more) to get all the coolant in.

If you're doing all of the above, and you're still not getting cold air (or the AC compressor cycles on and off continuously) your problem probably isn't low refrigerant.

Unfortunately, the AC systems on cars these days are three parts technology and one part voodoo.

Good luck!