cmogletree-
Go to Activities > New Activity and click on the ... next to the Priority drop down, this will open up a screen that will allow you to add/modify the priority drop down. A work order is a type of activity so making this change will also affect your work orders.
-Michael
Michael Melo
Product Manager
Method Integration Inc.
Website: http://www.method.me
LinkedIn: http://www.linkedin.com/in/MichaelMelo