I just got finished installing my first security system. And let me tell you, if you don't have a detailed listing of the existing wiring, it's gonna take you a while. The system I installed took about 10 hours, on 2 different weekends, mostly because I had to meter out every connection, and then repeat the process because the system kept going off. Once I had a detailed wiring diagram, it made it easier, but it was still very involved.
You have your choice when selecting your system of course. This system had a pager unit, shock sensor, stater interupt, etc, etc. We chose not to use the starter interrupt, or the auto window down output, and a whole slew of options, but it still took forever. And this doesn't even involve what I had wanted to do with the system. No computer integration, I'm afraid. Not yet at least. And of course, a remote disarm for myself of course....(It's not my car. )