Hi Steve,
Here is a link to the MARS 22 install manual : MARS-22.pdf
The first thing to watch out for during the remote starter removal is a Starter Kill / AntiGrind relay circuit. This is optional but might have been installed. The truck starter wire is Yellow at the ignition switch and as long as it was not cut ( interrupted ) and the Mars thick Green Starter wire only connected to it, you should be OK. If it was cut, then it must be properly reconnected as part of a complete de-install.
The other thing to watch for the the Passlock2 immobilizer bypass. There are many ways to bypass the trucks Passlock2 system including a bypass module, a pair of relays & a resistor, or a more permanent solution. Find the MARS 22 Orange (-) Output When Activated wire and see where that goes. Some Passlock2 bypass modules cut ( interrupt ) the Yellow Passlock resistance wire and it must be reconnected after bypass removal.
You can do it hot. Most professional installers never disconnect the battery during an install. Just make sure you don't ground your cutters or a wire to chassis metal during removal. As for the airbag, be careful around and do not disconnect any yellow shielded wire harnesses. These are usually found along the steering column and under the dash.
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Soldering is fun!