it is difficult to rent a van in Shantou? how much they charge for a day or per trip (2 way) ?

It may be a little hard for you to rent one upon getting there, especially you don't speak Chinese. Well then, I have two suggestions:
1. If you have booked a hotel there, ask your hotel for help. They would rent a trustworthy one for you. I remember the fare is CNY500-800 per day.
2. Try to search Ehi Car Rental Service online to consult whether they would help. Good luck.