How to service EVAP system...

Ok, here's the situation...my "Check Engine" light has been on since I bought my '96 S10. It has a 2.2 and gets really bad gas mileage, even though it is a stick shift. The scan tool says it is reading codes from the EVAP system, something about a vent malfunction or such. I tried looking it up in the service manual, but it only says to have a dealer service it. It sounds like it could either be an electrical problem with the vent, or the vent is blocked. Either way, I have to take it apart and find out. Since I have never worked on it before, any advice would be greatly appreciated.

P.S. I do know about electrical since I am training to be an electrician, but as far as this system goes, I'm not sure how it is set up, but I can do the work myself.

check for any cracks in the purg lines most of the time you wouldnt find one on a good day. second you will have to drop the tank and replace the pressure sensor on the top of the tank. I would replace the gas cap as well

Replace the fuel tank cap.

On lots of occasions the cap not sealing properly will cause the code. This code will not cause bad fuel economy though.

You have to do a tuneup including:

New plugs
New Wires
Cap and rotor (If applicable)
Air Filter
PCV valve
Fuel Filter
MAF Sensor cleaning.
If over 100,000 miles you should replace your O2 sensors.

Without retrieving the stored error code(s) you're really just chasing a ghost. The PCM is trying to tell you something by illuminating the "Check Engine" lamp. All you have to do is listen.