Axle Ratio Change '04 TJ

I got my "build sheet" from Jeep and I have a 3.07 axle ratio and an 
Anti-Spin Differential Rear Axle. This is in a 6cyl Wrangler with no 
lift and 225 75-16 tires. I'd like to have a 3.73 axle ratio so I could 
use 5th gear for something more than flat highway driving. Do I need to 
do anything more than change the differential (front and rear) gearing? 
And if anyone has had this done what am I looking at for price?
-- 
FRH