Toyota Repair: 2001 Toyota Corolla P0440, fuel tank cap, charcoal canister

Question
I own a 2001 Toyota corolla with only 74,00 miles on it . A light came on P0440 ( replace OEM gas cap won't fix) and took it to a dealer. They told me that fuel filler neck need to be replace and going to cost $360.   I live in Vegas where the weather hot 300 days in a year. Is it too soon for that fuel filler neck to be going out and how hard is it to repair it myself?
Ken

Answer
Here are some of the things that the manual lists that could be the problem:
 Hose or tube cracked, hole, damaged or loose seal
 Fuel tank cap incorrectly installed
 Fuel tank cap cracked or damaged
Vacuum hose cracked, holed, blocked, damaged or disconnected
 Fuel tank cracked, holed or damaged
 Charcoal canister cracked, holed or damaged
 Open or short in vapor pressure sensor circuit
Vapor pressure sensor
Fuel tank over fill check valve cracked or damaged 
ECM
Evao system leaks can be difficult to diagnose, the best way to check for a leak without just starting to replace parts is to use a smoke machine, this injects smoke into the system and pipoints the leak or the system can be prssure tested using special equipment.