Tell shop it’s at to replace the crank sensor with a good one, clean any oil from harness connector (behind driver side head) and make sure it’s not close to exhaust or otherwise shorting out somewhere, check all ground straps, and make sure they installed the heat shield and spacers correctly. If it runs well afterwards and fixed it then take the invoice to dealer and ask for partial reimbursement perhaps? At 20 years old as others said, dealer is no longer best equipped with techs who are trained on these trucks anymore. Same goes at all dealers as vehicles age.