I have recently just "patched" two buildings together for my work so we could save money on Internet connections. We originally had Cable Internet running to both buildings but found we didn't even come close to using all the bandwidth. So we looked at ways to interconnect the buildings. What we ended up doing was buying a wireless B router for one building (where the cable was going to stay) and a wireless B access point for the other building. At first we ran into difficulty getting the router and AP to "talk" come to find out what was holding us back was Mac addresses. We where informed that our router had an "unrecognizable" Mac address that was keeping anything from talking to our ISP. What they suggested we do was Clone the Mac address on one of the computers that used to work on cable (every router wired or wireless is capable of this) after that we have had no problems we have been able to flawlessly make two separate wired networks one. You are basically doing the same thing, making the Internet fly through the air to a wired network. I hope this helps.
Specs: ZONET ZSR0104WE (router)
ZONET ZEW3000PF (WIRELESS AP)
If you or anyone else here needs more help or specifics you can contact me at email@example.com
PS we used Wireless B because the internet will never reach or exceed 10mbps (highest I have see is 800Kbps not even a 10th of the capability of the router/AP) in our lifetime so save some money and go with something that been around a few years.