The whole dash assembly up front should be the same. I've got a TTQ Coupe so from the front seats back it's a bit different. I'm taking tons of pictures of the install. I'm installing it in place of the CD changer which is in my rear side panel.
All TTs have either the Concert or Concert II (2002 and above) systems. The Bose system was an addon on top of that. I'm not sure where your amp is, in mine its supposedly in the right hand side rear side panel. I'm not going to touch it though.
I'm using a Blitzsafe adaptor that I bought at Enfig Car Stereo (enfig.com - I highly recommend them). It plugs into the CD changer port that runs up to the stereo as I want to keep the stock audio system.
My screen actually ended up fitting where I wanted. It's not mounted but I had to remove the knee bolsters (4 torx screws on each side). I'm going to remove the ash tray and mount in between where it was and the center tunnel. I'll make it fit in a bit more with a bit of color match vinyl/leather.
I'd like to do a custom bezel but I don't really know where I'd get that done - I don't have the time to do it myself - plus it'd probably turn out like crap.