Welcome Dan. You'll find a lot of helpful people here.
Re the wiring diagram, you will find one in the Haynes manual for the Commando, which despite some faults is worth having. About $20 I think.
For wiring diagrams, I particularly like the large, color, laminated ones that "Prospero's Garage" sells. They're about $18 I think. You can get them on eBay, and probably elsewhere - Google that name and I bet they come up.
If you're new to British bikes, remember they're positive ground and RED IS GROUND, black (and a few others, like white and brown with blue stripe) is hot. If you're used to red/hot, black/ground, it takes some getting used to.
Good luck, and again, welcome.