just as clarification... the linksys will work fine as previously suggested, use it only as a switch/wap
log into the linksys, and give it a static IP address on the LAN (note, nothing you do will be with the WAN, only the LAN), usually the modem for DSL would be something on the 192.168.1.X range with X = 1 or 254 (usually, this may not be your case, go to start, run, type "cmd" and enter to get to a command prompt, and type "ipconfig /all", that will tell you)
after the static IP, disable DHCP, and connect an ethernet cable from any of the numbered ports on the 2wire, to any of the numbered ports on the linksys. I would also enable Wireless Security WEP or WPA/WPA2 (WPA/WPA2 preferred with a passkey)
after that, the linksys should pass through the 2wire DHCP, and work just as a dumb wireless access point, using any security protocols you've implemented.
This can be done with most wireless routers, not just linksys.. I have a linksys, belkin, d-link.. they all work basically the same. And, if you give the linksys an IP address in your range, you can edit it whenever you need to, to adjust security.. you just can't disconnect it from the 2wire without giving your computer a static IP, as it won't be handing out addresses anymore.