For the price and effort, just buy the LED version, youd be hard pressed to beat that. Think, 2 mins per led conversion = 640 mins, plus cockups and curcuit mods.
It would be possible, but bearly. You would have to modify almost everything. And chances are the cost of buying 320 loose leds of any color would exceed the price of a set of LED lights from the store. Its after Christmas now, lights areound here are cheap. Me and the wife got 4 boxes of LED lights for less then 20 bucks on Saturday.