Personally....I think any aftermarket replacement steering or suspension parts are junk if they are not MOOG........and I think your quote seems a little high....If those 4 parts were a hundred bucks apiece ( which they are not) and the labor was a hundred bucks an hour.....that would come to $750.00.....them add 80 bucks for alignment and then tax.......Looks like they are about right except the parts are priced a little high.......If they are using original GM stuff it would be close though.