i put my g to a smoke test at pepboys today.

As a result i was told the canister and the purge valve needs to be replaced. And i have 2 questions about it.

1) a friend of mine told me that a smoke test needs to be done with a computer and they need to on/off the canister. Since they did not do such a thing, it might not be the canister could be just the valve he says. Who do i trust in this case?

2) if both needs to be replaced, do they need to be oem or aftermarket would work? if so, what are the part numbers?

Thank you.