K, high school electronics isn't going to help with micoprocessors, everyone who has taken time to learn them recommends them for everything! They are pretty cool though, just leave me a bit cold right now... In the future maybe. For now though you could search for a pic calculator online, I'm sure I have seen one for flashing leds, but if you do you'll have to configure it to (oscillator, wdt, mclr etc). You will also need a means of compiling and programming the code.
For now though here is an idea which may work: a 555 oscillator working at a low frequency (flashes per second = frequency in hz, so about 1 or 2 maybe). Have that feeding a decade counter, either have the first three outputs flash the LEDs and the other 7 common, that would give u three flashes and on for duration of 7 flashes. You would need transistor if switching multiple LEDs and maybe a capacitor to store charge on common outputs... Would that work?