Hello Anna,
GPS was not fitted to the Hyundai in 2008 in Australia, so can't help much, but try this, it MAY wory.
Disconnect the - (Negative) lead on your engine battery for at least 30 minutes, preferably overnight. You do not need to disconnect the + or positive lead at all. This should allow the memory in your radio to clear and when you reconnect the battery, it will hopefully clear the fault with your mp3.
The clock timing was an issue with that model but usually faulted when the car was new, not after 6 years. The reset, MAY fix this problem too.
You will of course, have to re-tune your radio stations.
Good luck.