You should join the Pam Clocks and Thermometers group on Facebook, there is a guy on there who can replace glass lenses with supposedly near perfect results. I believe it involves bending the metal edges around the glass back with a popsicle stick. I've replaced glass on Pam style thermometers with this method and had less than perfect results, but better than broken glass. For cleaning, I've dumped a bunch of Windex through the small slit in the back (for Pam thermometers) and it will pool at the bottom and flow through to the front where you can shift it around to somewhat clean. It's hard to tell from the pic whether you just have collected dirt at the bottom or more permanent imperfections, but it won't hurt to try.
