If you know that power is getting to the fuse box (if not, then nothing would work), then you must have a way of checking it. A simple test light is a great way to do it-hopefully that's what you have. If not, then go get one for less than five bucks, and google it, to learn how to use it; it should take seconds to learn.
Since you know you have power at the FB, go to the application (or directly in front of) and see if there is power in the wire. If there is, it is the application itself that is burned out/worn out, etc. I would guess that this is not the case since it would mean that BOTH items burned out/wore out at the same time. The odds of this are slim. If there is not power directly leading into the application, then work your way back to the fuse box, checking for power along the way. If there is not power at the application, you will eventually find a short in the circuit.
I would bet that, somewhere in each of these circuits, a connection has come loose. It may be related to the "radio-kype". I wonder, is there a junction box, or harness in the dash that came loose from the violent behavior of a stereo-theft, and that might have seat heaters/ wipers as a common denominator? If so, this is where you should focus.
Hope this helps.
"I can't believe I'm sitting here, completely surrounded by no beer!" -Onslow