WRENCHING - HOW TO

Has anyone done their own differential work? How hard is it to not screw up?

I have a '99 Expedition with a Ford 8.8 inch differential, 3.55 ratio and an LSD. I'm thinking after 260k miles the LSD is toast, and we are thinking about using it to tow our travel trailer too. I'd like to re-gear to at least 3.73 if not 4.10, and put an E-locker in it (maybe an air locker).

Anyone able to offer some advice? Recommendations on a Seattle area shop?