vanchopski:
Also, where did you find the info that pins Arduino (RS, E, D4, D5, D6, D7) interface with LCD pins (8, 9, 4, 5, 6, 7)?I found this schematic but I can't see that it provides this info anywhere.
You've got the first part backwards - Arduino pins (8, 9, 4, 5, 6, 7) interface with LCD pins (RS, E, D4, D5, D6, D7).
Sorry I'm late, Bill already answered the second part, but here it is again. On the schematic look at the IC in the upper right section. If you follow the wire from the RS pin (LCD pin 4) you will see the term 'D8' which stands for Arduino digital pin 8. The other pins have similar information.
Don