i'm no expert, but here's my 2 cents.
it's ok to bake ahead, but i wouldn't slice it until sunday, when you're ready to reheat it. it will dry out a little if sliced too early. after the ham has cooled enough to handle, wrap it in plastic wrap, then foil, and put it on a plate in the fridge.
to reheat, i would put the slices in a pot or deep skillet with just a little water, cover and reheat on medium low. don't use too much water, tho. you're not braising it, just kinda adding a tiny bit of moisture to help conduct heat and keep the ham from browning.
in nomine patri, et fili, et spiritus sancti.
Meh nom eh noh...doot dooooo do do do.