(2) The location of the library is marked with "△" as follows:

(3) The post office is in the northwest of the school and the shop is in the southeast of the school;

(4) From the post office to the school, walk 4 squares to the east, and then walk 1 square to the south.

So the answer is: (1) (0,4); (3) northwest and southeast; 4, south, 1.