I know this is an old question but it really wasn’t answered so here goes . Smoking the evap system will take less than an hour or time so depending on the shop rate you have an hour of labor and whatever part need to be replaced . It can be as pricey as a evap valve set that can be 2-3 hundred dollars to a vacuum hose that would probably cost a dollar or less if the mechanic is nice . To the other part of the question will it effect the car the answer is a bit tricky . For the most part no but there is the possibility it can vapor lock the tank which can make the flow of fuel difficult but thats usually when the gas cap is bad . Seeing that you replaced your cap this wouldn’t be an issue other than the annoying MIL light . I would suggest having the codes read occasionally. Seeing how the light will be on all the time you wont know when another issue may occur that could actually be detrimental to the car Hope this helps