I'm sure fedora has the drivers for boomerang/vortex based 3com nic's ... the module you'll want to load is 3c59x . I don't know the names of the start up scripts for fedora - but they will most likely be in something like /etc/rc.d or /etc/rc.x with x being the run mode. You will have to consult some other fedora users or a howto for that. However.. to at least test out the nic - as root type "modprobe 3c59x" .. then "tail /var/log/messages" which will show you the latest syslog. if it shows eth0 coming up and the driver loading then your nic is working.
Remember - if you are using a hub set the nic to half duplex mode using something like 'ethtool eth0 duplex half'.. hubs don't auto negotiate very well. however, its going straight into a cable modem or a switch then you can leave it alone and it will auto-neg and set itself correctly.
Also, I believe fedora using 'dhcpc' for dhcp (which a cable/dsl router/modem usually uses for assigning ip addresses) so an easy way to get an ip if one isnt assigned when 3c59x is loaded, is to type "dhcpc eth0"
The modem might be a different story. Linux is sketchy with winmodems because they sacrificed hardware performance for cost by using your cpu to handle the modem. Almost all recent conexant based chipsets are winmodems and have closed sourced win drivers - It's a difficult subject for a linux beginner to tackle but if you really want to try it then let me know. Otherwise, buy a hardware based chipset modem - they usually run around 80 dollars new, however - last time i checked.
Remember - I'm speculating on most of the bash commands heres, I'm not a redhat user and this is coming solely from my experience with solaris and slackware.
on edit: I found a thread discussing modems for linux...
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=240x671