if you wana be leet, you change it hot. pour a little oil through to run the channel to the plug clean, and some even drop the pan and clean the inside of the pan before filling. but my opinion for an average non-race car.. doesn't matter hot or cold, as long as its done without damage.
I would however highly suggest not using any automotive junk from walmart. It may not all be bad, but theres better ways throughout your life to save money. Not to mention good item or not, if you ever worked at or know anyone whos ever worked at walmart or a similar big box store, you'd never buy anything from them again.. unless its something non functional/unimportant such as a 'chair' or something else to rest your as s on. Tho ofcourse it doesn't need to be a bigbox store to have shitty stuff and policies, and there maybe exceptions but its a good rule of thumb.