Various monitor display problems

Lately my monitor has been acting weird, cycling from very dark to very bright, then going back to very dark, like the contrast is screwing itself up or something. The corners are displaying brighter than the center (almost like an inverted tunnel vision or something), and recently it has started displaying everything in a purple hue (as if I had removed all the green from my image display settings). This seems to happen at random and fixes itself sometimes, and needs to be shut off for several hours at others.

Is there any cheap and/or easy way to fix this short of buying a new monitor or taking it to be repaired?

The monitor is a 17" Viewsonic P775 if that helps in any way.

No. It could be a number of problems causing these symptoms, along with bad power to one of the colour filaments (the missing green you mentioned). This is not the sort of thing you can fix unless you're a professional at it. Get a quote from a repair guy for fixing it by all means, but expect to be shopping for a new monitor (the purple hue is the killer here - if one of the colour guns is gone, the entire CRT is as good as dead).