Great. Read the entire instructions again. You always pick up little things after you read a few times. I always do. You have the right idea. The only way to begin is to begin. If you don't cut or break anything, it's all re-doable.
It will be necessary before you get too far, to have all the components in place or available. Ignition switch, ballast resistor mounted to outside fire wall, coil, starter, alternator. Need to scope out a good place to mount the fuse panel and how you are going to mount it. (on a bracket or not, etc). You will have lots of questions, no problem, but so will we. NEVER be afraid to ask questions.
What have you decided on turn signals?
Do you have any gauges?
Here is the fuel gauge reducer if you get a 6V fuel gauge. You won't need the expensive Runtz type unless you have a radio or heater. Even then, you may not. (use a 12V radio and swap the heater motor to a 12V motor) Easy and smart.
DON'T install the fuel gauge or it's tank sender until you test them, with the voltage reducer, together on the bench!