Hi there,
If you're hearing a soft hum when you press the window switch, it sounds to me like the motor is good and it's the regulator that has gone bad.
In either case, I don't think that the motor from the '98 will fit a '94, but I could be wrong.
I think your next course of action should probably be to remove the door panel and vapour barrier to actually look at what's going on inside the door. Be careful w/the airbag(if there is one), and don't turn on the ignition with the airbag disconnected, unless you're willing to go and have the airbag light cleared.
Just my two cents,
Tiger