I need to change the fios quantum gateway routers's ip address to be able o connect via vpn to my office.
Look in the user manual on how to use a vpn.
or go to the vpn site on instructions on how to use with the Fios Quantum G1100
some services do not allow the use of vpn' s so that may be something to consider.
You'll need to talk to your office IT staff, do they mean that you need a static public IP?
If so, that requires a business account with a static IP. However this seems extreme, unless you work for the CIA or something most VPNs work without static IPs.