Jiuzhaigou -> Huanglong -> Airport?

Hi -
I will be coming to Jiuzhaigou from Langmusi. I would like to spend a couple of days and then hire a taxi to stop at HL before continuing to the airport.

Do you know how much this would cost? Also, the last flight leaves to Chengdu at 16:05. Would I have enough time to see the scenic area?

Thank you!