We traveled in a group of 7 to Hualien in mid march 2012. We did a one day tour of taroko (9am to 4pm) and also traveled from Hualien to Cingjing (9am to 4pm) on the second day.
I would like to strongly recommend my driver Mr Zeng (husband of Ms Gu, whom I understand is quite popular in this forum). He is a highly competent driver. He also tried to ensure that the trip was comfortable for my 82 year old grandmother.
He recently bought a new 9 seater car. It was new and comfortable for the 7 of us.
For booking, I communicated with Ms Gu via email (email@example.com) and also via the phone (+886-935-083-682). We met Ms Gu on the first day at taroko (she was taking another group of travelers) and she appeared to be very friendly and sincere.
For pricing, best to discuss with them directly.