Part 6 of the first generation uses the CR1620 battery
The first thing to do is drop the key. It has a latch (shown by an arrow)
The latch is fragile, so you need to gently push it.
The radio frequency has two latches on the end (indicated by the arrow)
They also need to be carefully guarded
It looks like a completely dismantled body.
Now you can replace the battery and reverse it.
