I did this and it worked (after loading it in Stick):
Start your camera directly into Play Mode by pressing the Play button or Play switch. Do not start the camera with the On/Off button - the firmware update method will not work if you do.
Press the Canon Menu key and scroll around until you find a menu item that says "Firm Update...". There are usually three or four tabs in the Menu (varies by camera). You can probably stay on the first tab (typically Playback Settings) but some experimentation might be necessary.
Select "Firm Update..." and press FUNC.SET button.SplashScreen
It should say "Update firmware version?" Press OK. If everything went correctly, the CHDK splash screen will appear briefly on the Camera's screen.
Go back to the camera mode and you should see some new OSD (on screen display) elements.
Activate the CHDK menus with the <ALT> key or key sequence defined for your camera.
very happy to have CHDK again and raw capacity, only wish I had exposure control.