Hi mate,
Yep your going the right way about it. Obv you immobilizer will be permanently deactivated.
And the wiring, yes, it just connects into the existing wiring. However, i don't recommend using connector blocks, its much better to actually solder the new wires onto the existing wires. this prevents them from possibly working loose over time and a better connection.
I normally find the correct wire, strip a cm piece of insulation from the wire, wrap the new wire around it tightly, and then solder it into place. Then use some heat shrink tubing to tidy it all up and re-insulate it. Do that to each wire and your done.
Hope that helps mate,
Alan