Messed up ignition timing...NEED HELP ASAP!!!

Today my dad was fixing the water pump on his Mitsu truck and when he was taking off the rad. fan cover or something he must have messed up his ignition timing.

It's a 4G64 (that's right...4G64 - not 63) 2.4L SOHC motor.

Can anyone tell me how to get the timing right again?!?!?!??!