If i were to reset my iphone 3gs would it take off my jailbreak?

I just bought this phone from craigslist & all the other persons stuff is still on it.

I don't wanna undo the jailbreak, i just want all his info off & set up my own apple id password since i don't know his & i want to be able to download my own apps. I also have no way of getting in touch with him.

So is there any way i can rest the phone without undoing the jailbreak?
Any info would be helpful, thank you

I think so, reseting the iPhone will reset it to factory settings removing everything except the apple apps.

Nope, it will update to 6.1.3 and you would need to jailbreak it again