You can clear the CEL by disconnecting the battery for 15 minutes or so. Alternatively it will clear itself after a certain number of engine cycles. Even Autozone should be able to clear the codes for free.

I don't remember my exact number, but I had a cannister code problem in my 99 Trooper. It happened after I overfilled the gas tank. I checked for loose connectors and hoses, as well as lightly tapped on the solenoids. After clearing the code with my scanner it never came back. Thus you might want to clear your codes and check for a simple connector/hose problem. Give it a few miles to see if the codes come back before spending the bucks for a new cannister.