I wish to replace my 17 inch NEC LCD monitor with a Staples 19 inch LCD monitor My computer is a Gateway Do I need to change any settings as the monitor keeps switching off

When you mean shuting off, do you mean the power light changes to the shutoff light or it just blanks out completely. If it blanks out completely, then it's probably a problem with the power cord. If it the light just switches to red or orange than its probably a manufacturer mistake. You shouldn't need to change any settings to switch monitors.

The answer is no, its not much bigger so you should be fine with the same resolution.

No change.