You can put one in there. Here's a
photo If you don't have a sunroof there is sufficient support for a monitor. Here's another
option if you don't have the sunroof. I think he paid $600 for the dealer to install
http://www.icon-tv.org/Overhead Monitors.1.html
I have a sunroof and the support is weak! I don't get rattles from it but the monitor vibrates. They have a fix using a new bracket but they only supplying it for the factory system...

The dealer gave me hell getting the resonance fix done trying to blame it on the monitor...until I provided proof that my monitor only weighed 2/3 of the factory monitor...After talking with the service manager I found out it was a lazy tech not wanting to do the work.
I paid a shop $125 to put in the monitor. After seeing them do it I could of done it my self. Here is a link to another armada owners video upgrade with some step by step.
http://www.geocities.com/armadafication/
They factory screen is like $1200 for the replacement so I wouldn't go that route. The bracket to fix the monitor shake is like $400 also.