Anyone replaced their Navman PIN 570 battery? Help needed...

Hi.

I've just bought a new high capacity 1600mAh replacement battery for the Navman Pin 570 (as the life of SatNav when out walking is pretty low & hope to push it up a bit longer) & want to put it in the unit.

Now, I know there's two small screws in the rear recessed hole where the aerial sits when not up which I've removed but to open the unit feels like something may break as still feels secure at the bottom of the unit.

So, has anyone out there done a bit of Navman open heart surgery & know the gentle way of prizing it open? Am I missing another screw(s) to remove and or is there a special / recommended way to open it up?

All help / suggestion gratefully received before I send my liitle soldier unit to the big GPS grave in the sky if the patient doesn't pull thro the op....

Hi i have just renewed battery in my navman pin 570 the hiden screws are at the bottom of the back of navaman under plastic stubbs break them out and there are your other screws to undo lever back of gently but firmly with fine edge of a knife or somthing simlarand then take out 5 screws on board to get to battery at the back of it install new one and reclose ur navman............think my navman has given up because new battery dont work but hope this sorts you out,,,,blue