Since stuff packs don't come with anything other than the items, I'm assuming you just need to make sure that none of the houses, workplaces, sims, etc that you play with have any of those items in/on them before you uninstall. Otherwise, you'll either end up with some strange default ugly furniture or clothing replacing the item that was erased, or the sim/building will become unplayable because it'll crash every time the sim walks by or the building is opened due to the code assuming a missing item still exists. For clothing, I'm assuming just the ugly default replacements (Same as custom content being deleted sometimes), but for buildings I honestly couldn't tell you.
Take this with a pinch of salt. I've never owned a stuff pack or tried to uninstall just one pack - just an entire game from a computer I was no longer gaming on that only had the basegame anyway.