I usually get good help from the parts counter first, the service counter can be a hit and a miss, especially if they don't know you, or recognize your rig.
In the '93 Factory service manual above there is a troubleshooting section under the engine section, w/a break down of all the codes and their likely causes. You might take a look at that before heading in, maybe print it out and circle the codes. The more info you take in the better your chances are at getting a tech to help.
