I'll be staying over at Chengdu for one night and leaving at 2pm the next day.

Take metro line 3 to Panda Avenue Station, Exit A. Then, change to bus line 198 to the base (about 20 minutes).

Back to airport, take bus line 87 to the zoo (about 25 minutes). Next, change to bus line 9 to North Railway Station (about 15 minutes). Afterwards, take shuttle bus line 2 to the airport (about 50 minutes). :)