Cost to replace a vent valve and charcoal canister on a 1999 Acura TL?

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The check engine light was on, scanner showed vent valve and or charcoal canister to be the problem. My car is 21 years old, only 150,000 miles. Told in no danger if don’t replace these two items, just won’t pass inspection. Car was just inspected so good for another year. Thoughts?