how to dismantle a 2003 merc c class key fob?

I have a new key fob for a merc c class 2003 and need to remove the circuit from the old fob to replace it in the new one
How do I remove the circuit from the old fob without breaking it
This is my only key
I can replace batteries etc and can see the circuit board but am worried about trying to force the board in case it breaks