Is it worth detailing before selling?
Usually, and it is one of the few things that reliably returns more than it costs. Say it is a pre-sale detail so the quote focuses on what buyers notice rather than on long-term protection.
What is paint correction?
Machine polishing to remove swirls and light scratches rather than filling them. It takes hours and is what separates a detail from a wash, so it is quoted separately.
Is a ceramic coating worth it?
It makes washing easier and holds gloss for years, but it is not scratch proof and it needs the paint corrected first. Ask what preparation is included, because that is most of the work.
Can they get the smell out?
Often, though smoke and pet odour take specialist treatment rather than a deep clean. Say what the smell is in your request, since it decides who can actually help.