FM Modulator on Lexus LX470 2 Antennas

I'm interested in adding an FM Modulator to the factory deck in my Lexus LX470 to incorporate a rear entertainment system that I put in.  I pulled the factory deck out (in dash 6 disc changer, tape & radio) and it has 2 antenna hooked up to it.  I've read that the smaller one is a diversity antenna that is mounted on the rear windows.  When I install the FM Modulator should I unplug the smaller antenna from the deck?  I'm just wondering if I'm going to have issues with static since one antenna will have the FM Modulator hooked up to it and the other one won't and won't be receiving a signal.  Any suggestions?  Also, does anyone know of anyone that makes a trim kit for a 2000 Lexus LX470 so I can replace the factory head unit?

Leave the smaller one plugged in, and use the larger one for the modulator---it'll work fine. It would also be a wise idea to set the modulator to a frequency that is not used in your area. You have a factory 6-disc, and you want to downgrade to an aftermarket radio? I've never heard of any dash kit for that car---you would probably have to fabricate something.