First thing's first: take out the battery. We don't want any electric juice running through the D5100's veins while we're taking it apart.

Especially not to the large-and-in-charge 330µF flash capacitor.

The 7.4 V 1030 mAh EN-EL14 Li-ion battery is used by the D5100, D3100, and the COOLPIX P700. Sadly, it's not compatible with other cameras in the Nikon lineup, such as the D90 and D7000.