I don't think there are any changeable fuses in the Box since it's not built to ever be serviced.
I hope your CPU fan is maintaining enough RPM's to keep cool since your are drawing from its power. Sounds like you got lucky this time but I would be a bit more careful throwing solder around a circuit board.
Just for insurance I like to put a piece of cardboard over boards if I have to solder on them and just leave a hole around where I'm actually soldering. It helps give you a safe place to steady your hand without bending, breaking, or shocking delicate parts and its even saved me when I dropped my hot solder iron on it while messing with the cord.