Car alarm

I just recently bought my car asked the sales man if my car comes with an alarm system he said it didn’t. He also told me they send the car to a third party to install one (viper alarm). I know the dealer charges a lot when it comes to installing alarms but I was wondering if I could go out and get the alarm myself and have it installed could I still use my original transmitter to activate the alarm or will I have to be using the transmitter the they provide me?