Questions about Point-to-Point T-1 connection into network

I have a few questions about a point-to-point T-1 connection between offices and how it ties into the existing network.  This is the current config:

Office 1:
This office currently has a DSL connection for Internet access.  From the DSL jack on the wall is plugged into the internet port of a Netgear FVS318 Firewall/VPN router.  Then everything else is plugged into the router (i.e. servers, workstations, switches, etc.) The Domain controller is located at this office.

Office 2:
This office has DSL for Internet access also.  It is connected the same way - DSL jack to the Internet port on a Netgear FVS318 Firewall/VPN router.  A VPN tunnel is established from this router to the Office 1 router, so users can access network resources, etc.

Now this is where I'm totally lost.  We are getting a point-to-point T-1 line and they are not supplying the routers.  My questions are: How exactly is the point-to-point connection tied in?  Do I need to get different routers and recreate another VPN tunnel?  Or how am I connected to the other office with this point-to-point T-1 line?  I'm not sure how the integration of this point-to-point T-1 line will change the topology of the network.