I just got a mp3 player..ive never had one before

Yeah! so far you are doing fantastic!

I have 3 mp3 players, iRiver takes about 40 minutes to charge. The other two take about an hour or longer. Your manual should give you an idea on the charge times.

Your files should remain even when your battery needs to be recharged. Similar to a camera that is loaded with photos, the battery just powers the unit, it doesn't effect what you have on it. You may not be able to use your player while it is charging, that too will depend on the brand. Of my 3, only the iRiver will let me use it while it charges.