The WRT54G is a neat little unit but it does not have a built in modem. You will need to buy an additional device to make this work but be careful as it will not allow you to connect a USB modem, so you have to have an RJ connection. I made the mistake of thinking that the word ADSL ready meant it actually was ready to connect to the Internet -which its not. I had to buy a westell 2100 router and suffer the pain of router to bridge config (requiring a firmware update) and not what you need on xmas morning last year.
Do yourself a favour, buy a slightly more expensive wireless router with built in modem and your on to a winner.