Complete removal of the bottom cover is not necessary, however if you feel you need to take the cover completely off the machine to complete your task it can be done by the following process.

You will need to cut the two green wires attached to the music player.

Then you will need to cut the white wire that leads to the battery compartment.

Finally you will need to cut the black wire leading to the battery compartment as well.

The complete removal of the bottom cover requires the cutting and soldering of wires. For help with soldering reference: Como soldar e dessoldar contatos.