Diesel combi pete

Hi every one. I recently had my fuel pump done, It had had a leak and was getting heavy to run. I had the pump sorted. When I collected it the chap that had done the work said the pump had not been alterd at all, yet they had sosay took it to bits to sort the leak, He told me it would go streight back onto the mark I had made and be okay. NOT SO ..I now need to time it up again as it is out, it runs but dead rough. I do not have the gauge for this, so I was wondering; if a vernier depth gauge would be good enought to do it, if I made the fitting needed ?? any one have any ideal on this point. Cheers all Pete