Aye. The switch reverses the polarity. So to test it really, you have to swap the test leads also. That is unless you have an autoranging multimeter. I don't know the fuse number, but they are labelled on the cover under the dash on the driver side. Since its switched power, that's where you'll find it.
I don't have the wiring handy, but the circuit is so simple that you don't really need it. Either there's juice at the connector, or there isn't. If the juice is there, then the problem is in the motor itself. If it isn't then you check fuses. If you don't find a burned out fuse, then you start tracing and Ohming out wires. That's when you need the diagram.
One other note, if you do find a burned out fuse, you need to figure out what caused it to go.. fuses are not maintenance items, rather they're safeguard devices.