Hi. A couple of things that might help.
1. We had multiple copies printing on laserjet printers. The cause was found to be the timeout setting on the network card/jet direct box attached to the printer. You need to set it as high as possible as the AS400 will resend each print as it has not received a signal indicating the print has completed.
2. Regarding the deletion of the output queues. If the queue is associated with a writter, you will need to end then vary off the writter BEFORE the system will allow you to delete the queue. Then use the WRKOUTQ command to display the queues and delete it from that screen.
Hope this helps