Have a system with 802.11 b/g installed. Is a wireless router, connected to my current DSL, all that I need?

Answer 1

That should do it..

Answer 2

yes, that should mean that you have wireless built in to your computer. try looking for someone elses signal.
go to network connections, click on wireless connection 1 (or which ever one you are using) and search for a networks. some or none may pop up but if you an do all the above steps then yes yo uhave wireless on your computer and you just need to oget a wireless router. (and an extra ethernet cable) and follow the directions and youll be online.