You'll be intimate with a wiring diagram by the time your done.
Not hard but a little time consuming to figure out all the wires, especially if you dont have a good diagram. You will def need to know you're way around a meter.
depending on what kind you get they have a lot of different options. The one I did has a brake switch cutoff, parking brake switch cutoff, can control the door locks, etc so it cant be easily stolen. You don't have to use all of them,
For bare bones operation all you really need to tap into is the ignition switch for start, run, crank, start/run etc, and the accessory wires if you wanna run climate controls or stereo. You'll also need to tap into something that carries tach signal, a fuel injector is an easy one but you could also tap into ckp or cam sensor.
Can program them to run for 10 minutes, 5 minutes, how long to crank, etc. The difficulty depends on the capabilities of the system you're installing. T-taps are fine if you do it right and makes it easy to remove later.