Use the plastic opening tool to pry open the device at the seam where the two halves meet, prying all along the sides and the top seams if need be.
Do it slowly so you don't accidently rip the ribbon cable that connects the digitizer to the motherboard, as well as don't completely separate the halves as this can tear the ribbon cable.
Locate the battery and then use your spudger to gently lift the battery, which is held to the case using a sticky pad, and free it from its position.
When you remove the battery, do so slowly so that the wires connecting it to the motherboard aren't torn. The wires will be disconnected in the next step.
Thanks Patrick. I'm using your guide for reference when opening my Nuvi 2495 LMT. The MicroSD card slot quit latching so I wanted to see if its gummed up or something else. I didn't know where to start aside from removing the screws on back. Now I know where to pry.