Pontiac Repair: 1998 grand prix gt, head gaskets, grand prix gt

Question
about 74 days ago i had to have the intake valve and head gaskets replaced. my car "died" again and had coolent and oil mixed, i called the shop that did the repair and explained what happened, the shop then told me that the plunham went,(not sure of spelling)  The shop where my car is at now, explained to me that this should have been replaced at the same time as the others is this right.  Another question is do I have a right not to pay my bill of $551.00 for a repair that was not done correct and only lasted 74 days.  Please help me I am lost

Answer
Hey Stephanie:

No it's a mjudgement call on the plenium. you can't tell just by looking at them most of the time if they are bad. I as a rule offer it to the customer as a replacment especially if the car has a lot of miles on it. It's a plastic piece taht had a tendency to warp over time. but to answer you question no it's not a required part to replace. unfortanatly you will have to pay for the repair :(  It technically is a different part failure should they have looked at it better when they had it apart yes but it may have appaeared okay at the time none the less.. Sorry to tell you the bad news :{ and good luck :}