What does your wireless router need drivers for? You surely don't have Mint running on your router. And to your wireless clients the wrt54g should act as a simple wireless access point. For configuration you'll only need the webinterface. So you won't need any drivers at all.
You're talking about the firmware for your wireless network card? If it's not possible to install the driver via the restricted drivers tool you need to download the firmware for the chipset used on your network card. Have a look at the wiki page for friendly wireless cards and compare with your wireless cards name. (Most likely something like linksys W**54G) http://linuxmint.com/wiki/index.php/Lin ... Wifi_cards