Head Unit Modification Advice

I heard that the Pioneer DEH-2900MP has empty spots on the board for adding an AUX input, and that you need to add a few resistors and capacitors, remove one IC, and change the value of another resistor. Since I’ve never worked with SMD components before, I’m not sure which size resistors or capacitors I should use. There are so many types like 1206, 0805, etc., and some say 1/4W. Which ones should I buy for this modification?