What is a purchase order from a car dealership?

I’m trying to change my own spark plugs for the first time and I’m a little lost. I’ve heard that I should wait until the engine is “cold” to change them, but I’ve also heard I should do it while it’s hot. I’m not sure which is true. Can I change my spark plugs while the engine is hot?

My seat belt is stuck and I don’t know how to fix it myself. I’ve tried, but nothing has worked. How do you get a seat belt unstuck?

How should I repair a scratch on a plastic car bumper? My kids were playing with their bikes outside and they ended up falling into my car. The bike left a big scratch on the bumper.