VPN-branch office to main office via DSL connections

My client has a main office with internal LAN IP addresses that are static 10.x.x.x and a centrally managed T-1 that I cannot touch for VPN use. I will use a DSL connection at the main office with a modem in bridge mode. The branch office will also have DSL. I want to use a VPN client on the branch office site, and connect to the internal network at the main office. The DSL modem at the main office will be in bridge mode and connected to a Linksys router. What do I need to do to get the Linksys router connected and/or passing VPN traffic to a 10.x.x.x IP address on the LAN? I am not sure if I need a bridge device between the Linksys and the internal LAN, or if I can configure the Linksys to handle this. If I need to purchase a specific device to make this easier or more reliable, my client is open.