Preparing for level 85

Honestly, there's not a lot you need to prepare for. You get an extra prize box in your dailies with some cool stuff, but it's not like you'll face new challenges. You'll just be better off.

I suppose credits. Taking a toon from 1 to 85 is over 6 million. Just make sure you're on a good guild with lots of raids, and you should be fine. Don't waste credits on mods that don't have speed showing.