Do you remember where you got the plans for this layout from? I'd like to go with a whole house unit at some point but right now an external setup like this sounds good. Thanks! FReepers are the best!
If you have experience in wiring and circuit boards, which I don't (not much anyway), then you ought to be able to fix yourself up with the help of the instructions included with the transfer switch.
Your local electrical shop will have what you need.
But it can be complicated and dangerous (the power surge that can come from the main transmission lines near your house, etc.) and a good electrician will fix you up for a few hundred bucks.
Worth it, and you can watch him and learn.
Best way to go is to get an interlock on the breaker panel. It’s a mechanical lock switch that only allows the generator breaker to be on if the main breaker is off. Then run the wire from the generator breaker to the outside of the house. I wouldn’t put a generator in the garage, to much fumes. Then you pick what breakers will be on in the house, with all breakers potentialy available.
I hook my generator up to an extra double pole breaker in the box. I turn off all the 220v breakers and most importantly Turn off the main breaker and power up the whole panel. That way i have power to everything but the hot water heater, stove and ac. This is not really the proper way to do it because if you forget to turn off the main you will be feeding power back out to the pole, creating a dangerous situation for a lineman. Then also if the power would come back on with main breaker on it’s going to feed back into your generator and ruin it. I hook it up like this during an emergency, but you have to be extra careful and double check that you hook up and turn off what needs to be off before powering up.