For the AOpen modem, go to this website: http://www.linmodems.org/
Download and run the scanmodem tool avaiable at that website. It will run tests on the modem and tell u exactly what chipset it is and will also make recommendations on where to get the driver from. You would need to build and install the driver and then use a dialer like kppp or wvdial.
As far as your internet service goes, you need to find a provider that uses point to point protocol.. avoid providers that need you to install special software like juno does.