I have a 2003 Toyota Echo with 155,000 miles. Until recently I never had any problems with the Check Engine light.A month ago, after the Check Engine light went on, a Toyota dealership said they found code P0442 P0456 and said my gas cap was cracked. They replaced the cap and charged me $21.23 for the part and $99.80 for the diagnostic. The light went off. Less than a week later, the light went back on. This time they said I needed to replace the gas filler neck. Parts and labor cost over $500. The light went off. 20 days later the light went back on. Now they say I need to replace the charcoal cannister, for an estimated cost of $839.Is it likely that all these were necessary? Am I being taken advantage of?Thanks,KenXXX@XXXXXX.XXX

Optional Information:
Year: 2003
Make: Toyota
Model: Echo