It is not that difficult to replace the water pump on your 2006 Cadillac DTS. You will however need a special tool to remove the pump from the water crossover housing. care must be taken when removing the pump. If you damage the cross over housing it will need to be replaced also. Also, don't forget to replace the water pump drive belt and check the tensioner.
HUGE JOB DID MINE LAST WEEK.THE HOUSING THAT THE WATER PUMP SITS IN NEEDS TO BE REMOVED.BASICALY EVERYTHING TO THE RIGHT OF WATER PUMP COMES OUT.AIR FILTER HOUSING COMPUTER NEER RIGHT STRUT.MECHANIC COULDNT BELIEVE HOW HARD IT WAS.MAKE SURE YOU CHANGE ALL 5 GASKETS.