Code P0449

My trusted mechanic was too busy, so against my better judgement I had my oil changed at one of those quickie tire places. My car listed above had 49,000 miles on it when I got it. I had already put about 6,000 to 7,000 miles on it and needed to get oil changed. They ended up changing oil, oil and A/C filters, checked spark plugs, rotating tires etc. Right after that I got a strong smell of gas in the car periodically. That stopped, but then after driving out of town on a bumpy highway my engine light came on. It went off on its own. Over next couple weeks I got I whiff of gas a couple times. I thought maybe it was bad gas. Went out of town again on same bumpy highway when I got back engine light came on again. This time I went to AutoZone and read code it was p0449. (Canister purge valve). My first question is: do you think it was due to something out of adjustment from that shop that worked on my car? Or maybe that's a coincidence and it's from driving 75 on that bumpy highway. Also, do you think this is going to be an expensive fix? Maybe give me a price range if possible. Thank you for your reply.