Is it ok to have more milli amps than necessary I have a camera battery that is 3.7V and 680 mAh Can I use a battery that is 3.7V and 800 mAh?

Probably. Put simply, the mAh rating is the size of the proverbial 'gas tank' the battery provides for your device. The larger mAh just means a larger 'gas tank'.

To be more precise: the unit mAh stands for milliamp-hours; it indicates that a completely charged battery contains enough power to discharge that amount of current for one hour. For example a 680mAh battery theoretically contains enough power to produce 680mA of current for one hour (though in reality, it might not be possible to discharge it that quickly) or 68mA of current for ten hours.