vpn connection

I’m am trying to set up a vpn between our office, and our software vendor’s techsupport office. I would like them to be able to dial in and run terminal services to work on fixing problems we have with their program. The problem is that we are both using the same ip addressing scheme on our networks. (192.168.1.0) Is there any way to enable them to connect via vpn? or do one of us have to change our addressing scheme?