How do you install door hinges on 98 Chevy blazser?

The factory hinges are welded in place. They can be replaced. The spot welds have to be drilled out and the new hinges are bolted in with backing plates. The cab side upper half of the hinges are the most difficult to replace. They require removing the entire dash assembly. There is a good possiblity that the original hinges can be restored by replacing only the hinge pins and bushings. The hinge pins and bushings are available at your local auto parts store. A good mechanic can do this with out replacing the whole hinge assembly. If the pins are worn beyond the bushings and have worn into the hinge bushing support some welding may be required to fill in the worn area.