Stone Forest will take the best part of the day. There are buses that can take you check with your hotel or negotiate with a Taxi. Taxi a little faster.

I paid about 400 RMB for the day to a taxi .Additionally went to greenhouse area( tons commercial flower growing companies) and the biggest Jade shop.I ever seen in Kunming.Visited Dali and Li Jiang in,it was fine and should be OK in December