Apple IIgs modem and s/w

[millerto@ava.bcc.orst.edu (Tom Miller)]

I'm kicking around the idea of buying a modem for someone who has an Apple
IIgs. Neither the computer nor the operating system has been
up-graded. It was bought about 8 years ago. 

I've talked to three salespeople, two handed me a modem off the shelf and said
the modem and the communications software would work. The third said an 
external MIGHT work with the proper cable but the communications software 
won't. Which story should I believe? Or, more likely, what is the right
answer?

I suspect that the modem will be used mostly for Compuserve/Prodigy/ Internet
stuff. Is that going to be a problem?

Thanks for your help.

Tom
millerto@bcc.orst.edu