For everyone's reference go to this link and scroll down a little. Gear ratios

It gives the ratio chart for both the 2007-11 3.8L according to tire size and gears, and then also for the 2012+ 3.6L Penstar. Just make sure you look under the correct engine AND transmission. The autos need bigger gears due to slippage. Anyhow since you are in the Dallas area you should be able to find a shop that will do the work cheap. A good price is about $200 per axle not counting parts.

As far as axles go- with 35's you should be fine. It's always a good idea to put gussets on your axle, whether it's a d44 or d30. They have the same problem there. Putting in sleeves is nice but not as needed unless you run 37 or larger. The shafts should also be fine unless you are using the skinny pedal too much or are in situations where your tire is spinning fast and gets sudden grip. Once again that can be mitigated by proper use of the skinny pedal. The harder you push your vehicle, the stronger the parts need to be. Hope that helps!