Unless you're pretty familiar with auto wiring, have someone install it for you.
Tie the door sensors into your dome light circuit. For your starter-kill, throw away any relay that came with the alarm unless it's a Bosch. Use ONLY a true Bosch relay for your starter kill. If you want to install a trunk-open sensor, run wires back to the truck light circuit.
You've got to bury the brain DEEP, so that a thief can't locate it easily. The best way is to remove the dash and mount it to the firewall, but that's probably a bit much for DIY. Take the glove box out, and bury up behind there.
Forget shock sensors. False alarm crazy device. If you do use it, mount it to the sterring column and test it by hitting the windscreen.
Don't use a NON-ECM SAFE test light in your car. Even older MB's have airbags and electronic modules on-board. And don't probe an SRS wire, no matter what kind of test light you use. The firing mechanism for the SRS uses extremely low voltage, and even a static charge can cause a bag to deploy.
Not to burst your bubble, but most driveway-install alarm systems slow even amateur thieves down for maybe a minute. If you don't incorporate the wiring into the factory looms, it's easy to find. That means your starter kill relay is vulnerable. Siren wires are found quickly, and the siren is almost a waste of time. Good security uses a pager and two transmitting antennae, or a phone system.
As to your remote start, I gave a primer on using a remote start in a Mercedes:
auto starter in 140 ?? experts chime in !