should i stay away from rooted phones??
one dude who wants to trade says its rooted.
You can always use Samsung Keis to flash the default rom which erases everything and bring things back to factory(out of the box). That's the 100% way to ensure nothing malicious is embedded.
Or you can do a factory reset from the phone itself. Not sure if it's 100% safe since a slightly differ rom could be already flashed.