Can vinyl siding be painted or stained, and more importantly, does it last or will I be repainting every year like a wood sided house?
Yes, you can paint it. Make sure you clean it very well (use a TSP Cleaner) and then use a primer first (although some sites say you can get away without a primer).
Also make sure to paint it a lighter color than the current one:
The expected life of the paint job will be dependent on the weather conditions for that area of the house and probably be about the same as a wood sided area.