If it were me I would not get the factory nav. I would buy this and mount my screen there.
You could buy a flip-out touch screen or mount a 7 or 8" with a little modiifcation i.e. relocate AC buttons and knobs, fiberglass and bondo.
It would be nice if you could integrate a computer to the touchscreen while keeping the touchscreen functionality and mod the factory Nav buttons to control you PC based nav. If you have the time, energy and knowledge then by all means pursue it - I am sure some members would be very appreciative of your efforts.
oh here is the link for that piecehttp://www.crutchfield.com/S-60LJMUQ...&display=L#Tab
'98 Acura TL 3.2 >Epia M10000 >512ram >200gb >XP pro>Lilli 619> Opus 120
TESTING as of 6/22/08 - Intel D945GCLF, 2GB RAM, 80gb HDD, XP pro SP1, same Lilli & Opus 120