I am a Nortel programmer with some NEC knowledge as well. I have a customer who has a Vodavi Infinie system and needs some basic changes made to it. Is there somewhere where I can find a manual on changing programming to the system and voicemail? I don't have any other info except that it's an Infinite system and it's old.

Check the manual button on the top of the page they should be available up there:

https://www.sundance-communications.com/installers/Telephone_Accessories/Manuals/

There were literally dozens of different infinite systems, so you're really going to need to get the model number from the KSU before you'll be able to obtain the correct manual.