[Andy10v]

I would not use stainless brake caliper mounting bolts, they should be 10.9 IIRC.

Depends on your tools, skills, condition of the calipers and if you want to deal with it. Are the pistons definitely seized? If may be they may just need the calliper carrier slides scraped clean, guide pins cleaned and lubed.

If the calipers are seized it might be worth checking the price of buying a refurbished caliper compared to getting yours refurbished.

If you DIY refurb the calipers and dont have an air compressor then get the piston most of the way out on the car before you remove the caliper.