I can't help you with most of your questions but I can answer one. The more megapixels that your camera has then the better the pictures will be. The more megapixels then the higher the resolution and the more detailed they will look.
I forget where I read it. I think it was on
www.circuitcity.com . They have a little "Learn about the Basics" guide for each area of items on their website. I believe that a 1 megapixel camera was designed to make a 3x5 picture look pretty much like a 35 mm...a 2 megapixel camera make a 5x7 look like a 35 mm...and a 3 megapixel camera make an 8x11 picture look like a 35 mm shot. If you enlarge them more than the guideline I listed then the pictures start to look grainy. I may be slightly off with the ratios but you can check it at circuit city.
Hope this helps.