What type of modem is it? If its a hardware modem then its simply a case of plugging it in and using the correct /dev/ttyS, if its a 'WinModem' then you might have a battle on your hands. If you post an exactly make and model then I'm sure someone on the forum will have battled with it in the past.
When you say install the graphics card - do you mean setting up X so you get a graphical environment, not just a command line? If so what distro are you using - the config command change between the distros.