Hyundai Repair: Price quote, hyundai elantra, emission control system

Question
A check engine light appeared and I had it diagnosed at an auto supply store results - large leak exists in the evaporative emission control system. Do you know exactly what this means and how much it will cost to fix it?  The car is a 2001 Hyundai Elantra  with 59,400 mileages.  

Answer
Presuming this is a code P0455, this code very rarely occurs for a reason other than an improperly installed fuel cap.  Make sure the fuel cap properly threaded into the filler neck, and disconnect the battery for about 5 seconds to clear the lamp and trouble code.  If it stays out for a week, the fuel cap was probably the issue and the lamp will most likely not return.

If the lamp returns with the same trouble code, the system will need to be diagnosed to find the problem.  The failure would fall into one of two categories:
1.  the purge valve is stuck shut, preventing engine vacuum from reaching the fuel tank; or
2.  there is an actual leak in the fuel vapor management sysem which needs to be located to determine the necessary repair.