My 99 subaru forester has a air bag light on is this a stealership trip or is there a way to diagnosis it

you could get a 12 dollar OBD usb-cable (k-line) from internet and use FreeSSM to check the computer.

There is a small black connector under the dash and one of the pins can be jumped to ground to make the Airbag module flash the codes via the airbag light on the dash. I don't remember the exact pin off hand but can look it up later.

 

Most common reason for an airbag light is a bad clock spring behind the steering wheel. This can also cause the horn and cruise control to not work.