as for redhat, i am not sure your hardware is supported, but if it is, the dial up modem should be mapped as /dev/modem . if u need to go on the net with it, install kppp (if not installed by default) and start it, it's pretty simple to work with
as for the network card, again donno what brand it is i can't really help. if it's compatible, u can try to run /sbin/ifconfig and see if you have a dhcp IP already, if u did, you're connected. if not, i donno, i guess someone can help u here.
can't help u much but did try to give u a hint to start