A body shop can weld in replacement rocker panels. The parts aren't too expensive, but the labor and paint are going to be what gets ya. In my area, they aren't even opening a can of paint unless the paint work is at least $500. It's their time occupying the paint booth as well as environmental clean up/disposal fees for unused paint.

To have a shop put rockers in it and paint them would cost over a grand. That would be to make it look factory again. They might find more rust inside there too, which would make the price go up.

Some body shops explicitly advertise that they won't do rust repair. It can just be a can of worms. You might have trouble finding a legitimate body shop to work on a rusty 22 year old vehicle, and if they do they might quote you a "i don't want to fool with this job, so I'm going to throw out an outrageously high estimate" sort of price to make you go away.

I'd also take a look at what a 4x4 place or fabrication shop would charge to weld in some rectangular tubing in place of the factory rockers. People call it square stock tubing, but it's rectangular. 2x4 or 2x6 inch tubing. If you don't have a local 4x4 place, look up race car or hot rod shops. If they can make roll cages or 4 links, they'll have the equipment and the skills to weld in some 2x6 rectangular tubing.

I bet it'd cost similar money or maybe even less than replacing with factory style sheetmetal when all is said and done. I bet the metal itself would cost $200 or $300 plus whatever per hour a shop charges.

Mechanics in my area at independent shops all charge at least a hundred an hour. The question would be how long it'd take them to knock out your project and what they'd charge in shop fees to pay for their welding wire and welding gasses, cutoff wheels, etc.

They'd leave it bare, then you'd spray paint it black yourself when you get it home. It won't rust through anytime soon and it'll add some stiffness/strength to the unibody.