You can update to iOS 7, but there is no current jailbreak.
For unlocking, call Sprint and ask them to unlock your phone, provided you have been a customer who has paid on time for the last 90 days and are not in a current contract (with this phone).
If all is good, Sprint will unlock your iPhone for international use only. You cannot and Sprint will not unlock your iPhone so that you can take it to another US carrier.
There is no legitimate commercial unlock where you can pay to have the phone unlocked by a third party. Sprint does not allow it's IMEI's into Apple's domestic unlock database.