Is $500 to replace water pump and hoses a fair price?

yea!! you know where that dude is!! .. look up Chilton or Haynes or look at it on U tube! yep it is fair if it was done right ,,you should have sent new timing chain,, tensioners and seals for the cams and crank and gave him another hundred !! then you would have been good for another 100k! look up water pump 2000 Cadillac 4.6 ltr