Changed the belts on time work truck today which is a 12 with the 3.7. The serpentine belt and tensioner is a piece of cake. The ac belt is a bit of a bugger to get swapped. You have to put in on the inside in the balance and then get it on the compressor. From there you use a zip tie to hold it to the balancer and turn the motor over with a bar until it is seated in the balancer pulley. After the first time it makes sense.

I changed them because it had a slight whine or whimper. That didn't fix it entirely, I think the alternator is getting a bit noisy but it did quiet down the front drive.