That's likely just a personal choice of the past owner (wheels) nothing to worry about there. Yes, they're likely to have sold them or done a trade with the wheels dealer. No, if it's a fairly new car there shouldn't be any other swap outs. If it's a performance car it may have been "chipped" which means the computer has been tampered with to give it greater horsepower. Generally, the past owner is very proud of that and will advertise it as such. Stay clear of those cars. They're likely to have been thrashed.