where is the evap canister purge/solenoid valve? and how hard to replace?

It was mostly likely on when the last owner had the vehicle they probably erased the code to make the sale. But it's not hard to replace at all.

This valve is above and behind the left (Drivers side) rear tire. Jack up the car, support it, pull off the rear wheel, and look to the rear and slightly up. It has two screws and one electrical connection and one vacuum hose. Took all of 20 minutes to replace it. Got new part on line at Amazon and saved 50%. My check engine light was on for over a year and the codes were telling me it was knock sensor...wrong...it was the purge valve.