Handy guide for what to expect when going for bigger tires:
Disco Tire Fitting Guide
As for performance upgrades, anything under 33" doesn't really require any modifications of that caliber. HD axles, CVs and gear ratios are only worth considering if you've decided you're turning your truck into a dedicated trail rig.
Wheel spacers might be a good idea to give you a bigger footprint and help potential rubbing inside of the fenders. On the upside, spacers will always be good if you decide to go a bigger size up. Check for legal issues with them in some places though, especially if the tires exceed the wheel arches.
