i have a 2012 land rover sport giving issues. i get a message to check fuel cap to see if its properly locked, (obvously i checked but it was fine), kept drivivng and around 100 miles later same message followed by check engine light. p0442 for very small leak in evaporative emission system . also, when i fill the tank up completely sometimes the car will die right fueling, but turns back up immediately. mechanic told me that most likely it will be the canister purge valve, around 120 dollars new, plus labor, but i dont want to mess with it before getting feedback. please let me know

 

What your mechanic says is very possible. If the Purge Valve is stuck open, it will fail its leak testing. Also, when you refuel, vapors are supposed to be forced through the carbon canister where they are stored. If the Purge Valve is stuck open, those Vapors are forced up to the engine where it actually floods it out.
If that is what is is, its a very simple test. With the Valve's electrical connector unplugged, it should be complete sealed. So removed from the vehicle, you should not be able to blow through it. If you can, its stuck open.