I've moved into an office with a Comdial DX-80 phone and do not have instructions for changing the user name on the LCD--Help!

Thats actually an administrator function. You can program it using the DBA programming software or through telephone programming but you need the programming manual. Chances are this system is not setup exactly the way you'd like so it would'nt hurt to have a local Comdial dealer swing by and take care of the names and any other programming issues you may have. They can probably show you how to change the names yourself. Here is the DET user guide if you dont have one already.

https://www.acccentral.com/DET%20User%20Guide.pdf

Read the rules! System programming steps are not to be posted on the open forum.
Mark