To instal new dashboard lightbulbs, first you need to buy the bulbs. I bought these ones from ebay: http://www.ebay.com/itm/400428841903
They are the exact same size as the original:
Remove your dashboard (don't worry, it's easy) following these instructions:
http://www.toyotavantech.com/forum/showthread.php?63-How-to-Remove-the-Dashboard&highlight=dashboard+removal
pop out the four lightbulbs with green markings on the back. Then remove the bulb from the grey housing. This can be tricky... just grab and wiggle the bulb with dry fingers and it should come out.
Next, just put in the new LED bulbs. The LEDs only work in one direction, so if the bulb doesn't light up when you turn the lights on, then unscrew the grey bulb housing and turn it 180 degrees and put it back it.
Put the dash back on and you're good to go!