usually they are little 194 "wedge" style bulbs or there are even some that are a little skinniner that I forget the number. I haven't done it on my F350 but i've done them on my ex gf's taurus and my old ranger I used to have. It's usually pretty easy, just get the cluster out of the dash and then the clear lense either "clips" off or has a few small screws in it, and open it up.
It's also a great opportunity to grab a micro-fiber towel and some spray detailer and wipe all the dust out of there that accumulates over the years!
whichever bulb style they may be you can find them at any auto parts store!