WARNING !!!

you cant hook up LEDs to 12V like you can an incan. bulb - they have to bne
current limited via  resistor somewhere or they will go ZAP!

typically 50 mA max or something like that...

still doesnt address the issue of how they got burned out, putting the 
'wrong wire' somewhere wouldnt change the resistor in any way i can imagine

i think joels on the right track with the voltage regulator -
before you buy one from VW for $150, post the specs on it - I bet i have
the component in my collection and can send it for 29 cents

:-)