Ausatco,
BoeingBoy should have no trouble just using the wireless modem/router to do what he wants. 802.11g and 802.11b are compatible with each other. So there is no problem with mixing and matching there.
As you said, BoeingBoy can connect to the router with his notebook via a CAT-5 Cable and configure the router.
Then, it is just a matter of moving around the area with the Notebook (connected wirelessly to the network) to test the signal strength.
Take Care,
Richard