Hello and welcome to just answer. The dealer is most likely correct on this, but it could be a stuck open purge solenoid, so try replacing that first. If the problem persists, then the the fuel control valve is most likely the problem, and yes it is a non servicable part that is incorporated into the fuel tank. Here is the service info regarding this.
Case Number XXXXX Vehicle Issue Vehicle dies out when coming to a stop. | Purge cannister contamination;Verify the vehicle complaint. If the condition is worse after just filling the fuel tank, monitor the short term adaptives and see if they go highly negative when the condition occurs. If they are slightly elevated. Disconnect the purge solenoid and see if the condition is less frequent. If this is the case review the below recommendaiton. System or Component Die out / Stall;Group 18 - Vehicle Performance / Driveability;Yes - Intermittent Recommendation Remove the purge line and see if there is any raw fuel in the line. Also remove the canister and check for raw fuel contamination. If the cannister is saturated, replace the cannister and purge solenoid and check the fuel tank control valve and liquid check to be sure they are functioning properly,. Modification Date 07/11/05 8:48 AM
Checked a few other sources and basicly they said the same. They said the defective vent valve is the problem. contamitation of a valve that is suppose to support fume deplacement not liquid. It this day and time it is remarkable to me that you would enclose a 10 cent item in a $500 part (the tank) and have to replace all if small part fails. Why in the world would a manufacturer do that?