Drew, you have to go through the DVD menu on the touch screen.
I think it's behind "menu" or "info", then DVD and there should be a "eject" button.
BTW, when mine was in for maintenance I got a replacement and the 4-DVD box 2007-2008 was in the glove box. No need to say that I took all discs for a spin in my computer if you know what i mean ;-)
There were 4 discs: Europe North, Europe West, Europe East and a Lexus Maintenance (or was it Evaluation) disc.