I agree. You could also use two Cisco 1721s with a WIC-1DSU in each. Point to point is easy to do if between two locations.

You either bridge the traffic between the sites (uh not the best way to go) or make sure that both sites have different private network IP ranges and default route out the WAN interface along with static routes for the opposing networks in each router.

Example:
Site 1: LAN Block 192.168.20.x/24
static route: ip route 192.168.30.0 255.255.255.0 serial0

Site 2: LAN Block 192.168.30.x/24
static route: ip route 192.168.20.0 255.255.255.0 serial0