Go to a well known place for good installs.

Prices can be from 200+ depending on features like if you want alarm and keyless entry with it. How far you want to be able to start car. If you want 2way communication from car to remote

Id stick with viper, Python, compustar i think is another good brand.

Python – Security with Remote Start - Python 990 is what i have. What cant it do LOL.

Also keep in mind. Even the best alarm is only as good as the install. Have a bad installer installing top of line alarm it can perform like a ****