Hi,there
From downtown Chengdu to Sigunianshan, you can take buses at Chengdu Chadianzi Passenger Transport Station (成都茶店子客运中心). The buses departs at 06:30, 07:30, and 12:00 and runs for 5 hours or so at a cost of 62RMB/per head.
There are accomodations less than $350 per night of course. Hotels there won't be that pricy.