Your wireless card uses the b43 driver, as you said, but it also requires extra
non-free firmware. Your best bet may be to create a
customized iso image that includes the firmware to burn to a CD. Otherwise changes you make will not be persistent across reboots.
You may also be able to make a persistent USB install, not sure how to go about that with System Rescue CD though.
I don't think it has a GUI network manager by default. You could also include something like WICD if you created a customized version.
Otherwise look here for network setup:
http://www.sysresccd.org/Sysresccd-manual-en_Network