I'm looking to buy a car from carmax?

Carmax is a very large and reputable car dealer. They generally only offer good late model cars that have been cleaned, inspected, guaranteed, and come with a short warranty. They are very professional and don't haggle prices. You'll pay a little more than you might at a smaller, less reputable, dealer but many people (including me) feel the extra peace of mind is worth the extra money.

Regarding your old car, they don't really want it for their lot. However, they'll make you a low offer on it and ship it off to auction after the trade. You might do better by selling it yourself, and using the money as part of your down payment on a new car.

Any decent quality sales lot will give their vehicles at least a basic service before they put their cars on the lot. This way if a potential customer does peek under the hood and checks the fluid levels, the fluids are clean and the correct level. It looks very bad on a sales lot if the vehicle looks neglected.

The same goes with a vehicle delivery. They will clean/detail the interior and exterior so it looks almost brand new, even though it is a used vehicle.

Call up Carmax and ask if they'll accept the Isuzu as a trade-in.

Do yourself a big favor and get the Civic rather than the Focus, you will thank me in the long term.