well my car has an aftermarket alarm, so the factory keyless entry is not used. I totally removed the factory HU and the aftermarket works just fine. At least I was able to reconnect my dome light! But yes, if you have the factory keyless, you have to keep the factory HU intact behind the new unit. Just secure it with velcro or something on the hump behind the cupholder area.

Civichik, it should be the same for your year. Take out your HU and take a look.