Battery is not loading. Can't switch it on

Since that weekend, my SAMSUNG Tab 2 7.0 GT-P3100 isn't loading any more.

I also found no way to start ist, connected to the power supplay.

a) how can I start the tablet (for to save the data), when it is connected to the power supplay?

b) how can I repair this ? (changing battery? Where to buy a new one?)