Anyone know how to fix a Nintendo DS

I got a Nintendo Ds from my cousin it needed a battery and a charger. I got that but now the start up setting won't save. My friend said it could be the logic board or internal battery? I know Nintendo can fix these things does anyone know how much? Or does anyone know somewhere else trustworthy where I can send it and get it fixed without costing an arm and a leg? I tried by passing the setting by using one of those cards but it didn't do anything. Would it be cheaper to buy a new one or see if I can get this one reapired? If I do get a new one what would I do with this one is it just junk? Thanks people

 

Don't know if this will help but won't hurt to look into it. They have an 800 no# also.
http://www.nintendo.com/consumer/systems/selectds.jsp