Did he put the right amount of oil in??? If you have the HEMI it takes what 7qts to fill it. Ive taken it down to one oil/lube shop to do my oil and they only filled it up with 5qts, I caught it before I left as they only had 5qts listed on the receipt and made them add the additional 2qts needed.... It would explain your lack of oil/oil pressure. I'd go buy a few qts of oil and add about half a qt at a time until its full, be a quick way to see if the right amount was put in it or not....