Why do my low beams not work in my 1998 gmc sierra 1500?

Maybe I am missing something, but I would try replacing the bulbs. There's a very good chance it will work, and it is inexpensive and easy to do (if it only needs a bulb). Hopefully, you don't have to replace the whole headlight and can just screw a replacement bulb into the back of your headlight. That's how it works on my Olds Cutlass Cierra.