Usually is most cases you don't need to worry about resistors for the 2n2222 method on slim. Also make sure you get 0603 size LEDS, you may be able to get away with slightly larger but 0603 is highly recommended. I only say this because you say the LEDs are 3-3.6v LEDs which sounds awfully high for 0603.
As for resistors, if your not sure you can always use a LED calculator (google it).
But if your serious about modding it's probably s good idea to learn electronics math or more popular known as Ohm's Law. Just remember I = V * R, R = V/ I