Hey Harlet....Congrats on the '05 Treg.
I was considering something similar (but $$ was the main issue). You may want to consider getting an Alpine Media Hub -- as far as i know there are 2 a)VPA-B222 and b) VPA-B211A. The will both use the navigation screen. (But you may want to check which Nav you have--I think the CD version only has the Aux output.). The Hub can be hidded and can connect a back-up camera, DVD, Ipod (with add accessories), Sirius, and alpine nav. If you do a search on here and Vortex I think u will see pics from someone who installed it.
Also (if you have the CD nav) --- you will need Spockcat's A/V adapter and/or the Video in Motion (or try the 12v bypass)
This option beats ripping the dash apart and makes everything look factory.
Hope I was of some help.