Begin by disassembling the platform from the base.

Do this by first untying the belt from the platform.

Then remove the heated bed and place it to one side, you don't need to disconnect its wiring.

If you have the Pi Camera installed, unmount it also, again you don't need to disconnect it from the pi board.

Finally, remove the old HDPE linear guides holding the platform in place.

The platform should now be free for the next step of drilling the holes for the linear rails.