Hacked iphone 4 help!!?

ok so i bought a i phone 4 from a guy but he did not erase all of his stuff like lots of pictures,contacts,apps....and he made the phone in spanish witch i can read but i perfer english...anyways...he also changed the font to this wierd curssive witch i cant read...and the iphone's sim card is at&t and it is cut and hacked but i was wondering if i can restore all of the factory settings on the phone...and i know it would take out the hack mode but i know how to hack it back but i am worried about if when i facory set it back to normal would it damage the sim card that is cut??? or anything please fill me with details thank you