I found a 04 navi but my car is 08. Just checking? help a brother outt.

 

Also, hypothetically if I was to instead trade in my tl for an older model 6spd, is it possible for me to have the newer speedometer dash?

 

I dont know for sure but I can only imagine that YES they are different systems. Not only is the software interface different between the years, but the newer ones have a backup camera so that alone differentiates them. The navigation discs arent even compatible between the 04-06 and 07-08's. Play it safe and use one from the correct year otherwise your just gonna run into issues I would imagine.
BTW, nice avatar pic. You took a fuzzy picture of just the doors, and trees are in the way :-P

 

i LOL'd.

 

The gauges can be changed.

http://www.uniquestyleracing.com/20actltystre.html