I've had as much success with Cisco products as I've had with Airport Extremes - not good. Last a couple of months then need replacement. Personnally, I've been using a Netgear RangeMax Next Wireless N Router. Very happy so far.
I have a DSL connection. Just connect the ethernet cable from the DSL modem to the WiFi gateway. You may need to access the internal settings of your router to change the SSID broadcast, add security, check for firmware updates, etc.
I've had a number of issues with my WiFi gateways in the past. With this Netgear router, I have my Vista PC attached via Ethernet and my iMac connected via Airport. This way I'm able to quickly diagnose WiFi issues I have on my iPhone.
Yes that's a perfectly good router. Just follow the directions that come with the router for connecting to your modem. Make sure you set the router up with a password. Then just go to settings -> wifi on the touch and connect.
That'll work fine. It's pretty much the standardest wireless router in existence these days. Power supplies are flaky, though. I had two go on me. If you ever need an extra, I still have one around here.
I got a cheap ($40 or less I think it was) Belkin one from Walmart, I've had no problems with it and the setup was simple since I already have DSL, it was a matter of taking off the old modem and just putting the cables into the new one. I had it up and working in about 5 mins. As others have said, make sure you change the Admin name and password, it comes with info that shows you how although THAT took me a bit of time to figure out. Still you'd be surprised how many of your neighbors don't realize that they should do this and their connections are WIDE OPEN. Eeek!