1.You will need the AEBS model with the modem and antenna ports to connect via dialup.
2.There shouldn't be any problem connecting to any standard 802.11g (or b) wireless network with that particular card (in theory, at least...).
I'm curious, how much of a discount are you getting on this basestation? I recently purchased a Netgear Wireless-G router for 80 bucks, $60 after rebate. That's not too shabby for a 4-port 100Mbit router with a built in firewall, very nice range, and easy to administer (via a standard web browser)... but it doesn't connect via modem (forgot about that). Now that I think about it, if you must connect via modem, the AEBS is your only option, that I know of.
There shouldn't be any problems. However, unless you'll be networked with other machines via the AEBS, you won't come anywhere near experiencing full 802.11g speeds.