Vendors: Do their inventory respawn? I've been trying to do a ninja, but damn if isn't bloody hard to find throwing weapons, which respawning vendors should help alleviate a bit, otherwise I'll have no option but go mod something.

I think the inventories do respawn. I always buy Mystic Arrows from the vendor at Rattkin Ruins by repeatedly reentering his shoppe. That way I can buy a lot of them with one visit. Otherwise using bows and throwing weapons would be impractical since you don't find nearly enough of them.

The Wiz8 vendors will restock their inventories every day or so, although they don't always restock the exact same items. Still, any of them that offer ammo will generally have some more ammo.

There are also magic items that can help to solve the throwing weapon problem. I know of one 'boomerang' shuriken in Wiz8, and I would imagine that it can be found in the earlier games as well.

Three full camping/rest cycles to respawn.

Fyi Crock (swamp) is the best place to get ninja gear in Wiz8 but some items are not available for sale until later in the game.