Just take the output cable from the wireless access point and plug it into the "Uplink" jack on the router. On most Linksys switches/hubs/routers it's the last port which is shared (so it is either another port or the uplink port).

And the difference between 11a and 11b is speed. 11b has a max speed of around 11Mbps on paper, and about 5.5Mbps in real life. 11a roughly doubles that speed as I recall. There's also an 11g which offers speeds around 50Mbps.