HaveaMacBookProandaniPad. Mypreviouswirelesssystem, aLinksys, apparentlydiedallofthesudden. Reviewedtherecommendedroutersonline, thendecidedtochatwithaComcastperson. She offered that I shouldconsidertheAppleAirportandsaidthatitshouldworkwithComcast. I cannot get it to connect.
In addition, if it is a telephony type (CDV) modem with a built in backup battery, the recessed reset button on the rear must be used rather than just unplugging it from the power outlet in order to properly power cycle it. You'll need something like a bent paper clip or a pen tip. Depress and hold in the recessed reset button on the rear until you see the front panel indicator lights begin to cycle, then release. Now give the eMTA the time it needs to re-sync.
When using the Airport Express you must plug your modem's ethernet cable into the ethernet port on the bottom of the Airport Express and connect your devices wirelessly. If you connect your MacBook to the Airport Express using an ethernet cable, you can't connect to your cable modem. The Airport Express is a nice device but it has very specific use cases, so if you need to connect to your cable modem AND support other LAN ethernet connections at the same time, you need a different device, such as the Airport Extreme or Time Capsule, or a router from companies like Linksys or Netgear.
In your current situation, you simply plug your AEXP into the outlet, disconnect your computer from the cable modem, reset the cable modem per previous posts in this thread, connect the modem to the AEXP with an ethernet cable, and then simply connect to the AEXP with your MacBook Pro using the Airport icon on the taskbar. To further configure your AEXP, fire up the Airport Utility application and add things like wireless security and password, port forwarding, etc.
Mac OS X on a MacBook Pro comes with the Airput Utility already installed, it's in the Applications -> Utilities folder. If your Mac already does automatic updates, the installed version should be current.
While I agree that Comcast's support reps are clueless for the most part when it comes to Mac (and many other common things), that's simply becasue the reps have no idea, not that it doesn't work. Comcast could care less what router you have, it only has to support DHCP connections over TCP/IP and ethernet to talk to the modem and that's like every consumer broadband router on the planet. No clue what you mean by "dinged"...
As for setup, the included setup manual is fine for almost all circumstances. As for the Comcast specific stuff, all you do is power cycle or Reset your cable mode when you connect the AEXP, that's it as far as Comcast is concerned.