I believe you need usbserial.ko or something similar which requires a kernel partial recompile (I have a set of modules for mine, and they are available). Doing "lsmod" as root on your ubuntu system, or "less /proc/modules" should list the modules you need.

Generally, if it consumes less than 100ma, it can work without a hub to power it.

The /etc/ppp directory has some scripts, though you would probably have to create one pointing at /dev/ttyUSB0 or /dev/ttyACM0 or whatever. I haven't seen wvdial, but there is the original chat program which works for most things.