I would say definitely replace the tires that are on there as you have no history on them.

Next, I think takeoffs should be fine for you. Race tires last as long as you want to ride them. Some guys pull them off after 1 sprint, while others can run 6 sprint races on the same set. Just depends on how deep your pockets are lol.

Find a reputable racer (Shane Turpin, Daltin Dimick, Jeff Brown) and buy takeoffs from them. They can tell you exactly how many laps are already on the tires. This will allow you to check out tires before committing to a brand new set.