Thanks to all who contributed to this thread, it was very helpful. Here are a few more tips that I hope may help someone else out with this problem. First, since I've wanted to remove tamper proof screws on other jobs before, I finally decided to invest in a tamper proof screw driver set (about $27 at Home Depot with various size attachments). Once I had that removing the housing was a breeze. Second, my circuit board actually did have some corrosion, likely from water penetrating the unit. So I took some 70% isopropyl alcohol, Q-tips and toothpicks and cleaned it carefully. That seemed to do the trick. Also, in addition to the weather stripping others mentioned, I put some electrical tape overlapping where the gasket meets the display unit to hopefully reduce the chance of water getting in again. Finally, if after you've put everything back together and flipped the circuit breaker back on, the screen is blank, wait several minutes. I was just about to take everything off again thinking it hadn't worked when the display came back on one line at a time. It's been working just fine ever since. Good luck.