Leshan to airport

Hi, is there another option then to take the train to the Shuangli Airport? Do we need to buy tickets upfront or the same day at the ticket office in the railway station?
Is there a possibility to leave our luggage in Leshan station? We will be coming from Emeishan (after 3 days) in the morning to visit the Big Buddha and need to go the the airport in the evening.
Thank you!