Pontiac: waterpump replacement time, shadetree mechanic, gm dealer

Question
I realize that time can vary, but what is the longest time it should take to replace a waterpump on my 97 GrandAm, 2.4L? I was told 3 hours, then 3 hours later I was called and told that it would take six hours(they hadn`t even started). Well, it went past the six hours and was kept overnight.  I was not notified that they would be keeping it overnight and it cost me a days work.Initially, it was to cost a total of $300,but later was told that it would cost $118.95 for the pump and $354.00 for labor.( I did ok that cost, after they had it for nearly four hours already).  I did feel that was high, but I was willing to pay, because I really needed it done and didn`t want to invest another day of "down time".  My work situation is unusual and I make a weeks salary in two days.....they cost me one of those days and interferred with the other. I would never have approved the work had they told me there was a possibility that they would keep it overnight. Any advice?  Was it an unusually long time and high cost? It wasn`t a dealership either...it was Firestone.

Answer
I am a good shadetree mechanic and can change a pump in my 90 Seville in about an hour.  It's not very hard.  Of course in some cars it is extremely difficult.  By mentioning Firestone I just found the problem, unfortunately most of these places don't have specific experience with all cars, and most mechanics haven't replaced on all cars all the parts, so places like firestone are usually the last place to do things like this, usually a auto repair specific place would be better, that specializes in your make of vehicle, such as a dealer.  I can only imagine that there should be enough space in the engine compartment to maneuver easily around the pump since the engine is small.  
Wherever you go you should not have to pay more than 120 dollars or so for labor for a pump.  At a GM dealer they should be able to flip that thing out and replace it really quick.  Dealers charge by job though not by hours, they charge what the book says to charge for that job.  Good thing is is that in most cases they WILL know how to work on your car quickly and efficiently.