I have a Sony display and controls adaptor spare in the garage I could do you a deal on if you are interested, was fitted to my mini facelift estate.......now no longer required.
Dont forget, as i think i may have mentioned before there is no dispaly adaptor for the GID, so if you had the integrated phone HU (CCDR 9Whatever :question) that also works the OnStar system, you WILL loose radio/ CD info on the display.
If you change the head unit Traffic master doesnt over ride the non-standard head unit and you wont hear the annoying voice, you will however still hear the 'click' as it is still working., but you can buy a seperate traffic master iterface box to get it working again (had one in my Vectra SRi, and still got it somewhere)
*EDITED TO ADD*Just seen yours is a Facelift, and IIRC some of these dont have the stalk controlled trip computer its controlled by the head unit, so if you change it you will loose the computer.
Do you have the buttons on the end of the wiper stalk (right hand side)

??