Shouldn't be very much... You have an electric button for your trunk release, right ?? When I had an alarm installed in my G1, they just tied it into this button !! works great and didn't cost me anything extra !!
you should however, tap into the wire under the door panel, near the factory switch. Look at your Viper alarm manual and find out which wire you're supposed to connect to and just try it. It should work with no problem.