07 Impala - How to change Evap Solenoid?

How do you change the Evap Vent Solenoid on a 2007 Impala LT Flex fuel. Dealer diagnosed Large EVAP emission leak and estimates $250 to charge. I ran the diagnostics and got a P0455 code.

I can get the part for $25, but not sure how to replace. Do you have to drop down the EVAP Canister to get at the Solenoid?

if so how does the Canister unmount?

Trying to save my 81 year old Mother in Law a $250 repair if possible.

Thanks much!!

Did anyone test your gas cap to be sure it was properly tightened or if it was defective ? A bad or loose cap will trigger a P0455 code . You didn't mention the cap so I don't know if that's a possible cause ? Go to the following website for a better description of possible causes and hints for resolution of the code . Go to http://www.obd-codes.com/P0455 .

Thanks for the extra advice and the OBD web site. I just read it and added it to my bookmarks. It's my Mother-IN-Laws car and she had just taken it in that day for another issue and the check engine light appeared on the way there. Dealer diagnosed problem as evap solenoid for $115 plus $250 to repair. Ironic that she stopped for gas on the way there. First thing I'll do is replace gas cap..Seal looks worn!! I will then clear the code and let her drive for a while and see if it returns. I won't attempt to install the solenoid yet, the part just came in at Advance Auto. Thanks!!