You stated at the beginning that you have this HU so it should not be an issue. You are not doing anything with the Steering controls. It stay the same.
You have 3 sets.. Front.. Rear.. and Sub. You will only be using Front and Sub , unless you decide to amp the rear speakers for the passengers.? Do like 25-watts rms to those. You will or should have enough Speaker wire left, and I chose the 4 ch RCAs for future use on 4 ch as the amp kit has one set that can be used for sub amp