The alarm module is located under the console, in front of the shifter.
However, 1998 U.S. Sportages did not come factory equiped with a remote starter and keyless entry. So what you have MIGHT be an aftermarket unit or perhaps a dealer installed unit from a later year Kia.
You can find the electrical manual for the Sportage here. http://www.kiatechinfo.com. If you look up year 1998 you'll see that it's not a keyless remote alarm. But you can try a newer year, such as 2002, and see if it matches your installation.
And yes, you are correct. The airbag system has to reset by the dealer to get the airbag light to turn off.