I fix computer networks for a living and only do car repairs as a hobby - I must echo what others are saying - unless you have a couple weeks you can park this vehicle that you can learn electrical troubleshooting on, and following a wiring diagram - your asking for trouble.
If you simply don't have the money at all then go to a wrecker and cut the fan plug off an existing fan harness, unplug the fans on your car, plug in the wrecking fan plug and wire it directly to the battery with a switch, you can run the wires into the passenger compartment for the switch. then manually turn the fan on when you start the car and turn it off when you stop. Hopefully your diagram will show + and - on the fan.
It will probably reduce your gas mileage with the parasitic drain but it will keep the car engine from melting down while you screw around with it.
You need more than the wiring diagram you also need the diagrams that say where the wires are located in the engine compartment and what harnesses they are run inside of. Hopefully your wiring diagram you bought includes that.
I am very familiar with troubleshooting automotive wiring from a tech manual and going in cold this would be at least a 2-3 hour job for me if it wasn't the fan resistor (which of course I would check first). If I was a mechanic doing these all day long in a dealership it would be a 20 minute job because I would know exactly where all the failure points are. And yes I know that if it does take the mechanic 20 minutes to find it your still going to be charged book time of an hour or two or whatever it is - that is how service departments make money - it may seem unfair - but they do have to warranty their work and it is not uncommon for electrical problem fixes like this to fail again.
Most of the time when I've done these things if it's not an easy fix (like the resistor) I end up starting off by following all wiring carefully - about half the time the wiring is chafed, or melted on a header or some such, and even if you know a particular circuit segment is dead by testing with a multimeter, it still takes ages to find the physical wire and follow it through from the diagram.