In my opinion the best way to get there is from Seo-bu Bus station in Daegu. There are about 15 buses a day to the Haeinsa area from Seo-bu Bus Station. The price is about 7,000W. It should stop in front of the Gaya National Park building. Then it will cost about about 10,000W to get to the Haeinsa turnoff. Then its a 1 km walk to the temple and further to the other smaller temples. One of the peaks is 5 km from the Haeinsa museum.
Another way is Hapcheon. (DON'T TAKE THIS WAY) There are 3 buses a day that leave from Hapcheon so I strongly discourage you from using the bus station there. A taxi from Hapcheon is 40,000W.
I suggest spending at least 2-3 days in the small town next to Haeinsa so you can see all Haeinsa and the Gaya National Park have to offer. This is a very quite area. If you are tired of the big city this is a great place to go.
A perfect place for relaxing.The SPA valley has a bade pool, SPA, steam room, water park and a fitness center.
It also has a souvenir shop located at the first floor where you can purchase items such as armatheraphy, health products and character goods (eg. Sdalyi dolls - the character of SPA valley)