Speedometer Short

i was trying to install interior neons in my focus by running it through the headlight fuse so that whenever i turned on the headlights, the neons would come on...well...to make a long story short, i couldn't get that to work, so i had to install my own fuse kit and switch for the neons... however, after i did this, i noticed that my dash lights do not come on at all anymore, which makes it pretty damn hard to see how fast i'm going at night. any clue what i did? i'm guessing i shorted something out, and if that is the case, how much money am i looking at to fix this. thanks a lot, ben