Hello, I just purchased a used HP SB21 projector, and I was wondering about retrofitting it. I've heard it mentioned, but I'm not entirely sure to what extent this entails. Nor do I know how much expertise you must have to do something like this. What can be done to these projectors? I suppose upgrading the bulb might do something... this this the extent of the retrofit? Does changing the bulb increase the available resolution? Any assistance would be greatly appreciated. Thanks.