Update:
Got everything just about wired up. Horn and parking lights flash, remote is programmed etc, however the remote start does not work.
Everywhere online says to use the green/white tach wire behind the parking brake release. I am getting 28VAC at idle and around 3VAC with the engine not running from that wire. My remote start instructions say "You should see between 1-4VAC at idle." So, my remote start does not work and the error code I am getting is "Engine is already running" which makes sense, since the unit is seeing between 1-4VAC. Any tips? Do I need one of those tach inverters? Any other wires I should use?