Code P0440

Overall no problems on my 99 trooper. Besides the oil burning (which I have grown to accept) never had anything big go wrong. Today my CEL came on and the code was a P0440 Evap Emmission Control System Malfunction. Light was on for about an hour and then when started the car for lunch was off. My wife also just informed me that the Light came on a few weeks ago and was only on for a few minutes so she didn't worry about it. I have read that the gas cap can be a problem to get this code as well as the EGR. I recently cleaned the EGR and it looks good. Anything else out there that may cause this. Checked the gas cap and it looks good. I guess I could buy a new one. Only like $10. Sad to say but I am thinking about getting rid of the trooper soon. Getting old and the resale is just getting worse and worse as time goes by. Thanks for any info.

Also, anywhere to get a diagram on how to change the belt.
Thanks