Hi Jan, when it comes to cutting sheet rock (if price isn't an issue) you can buy a sheet rock cutting tool that works pretty much miraculously. Maybe you could even rent one? After that a utility knife with lots of back up blades is the traditional method.
You can mark the edges of the boxes with chalk, lipstick, or paint. Press the sheetrock against the box, and then cut out along the lines with a sheetrock saw.
Another way is to mark the floor where the studs/boxes are and measure up from floor to center of box. Apply sheetrock over the boxes, and then cut out using a Roto-Zip and straight bit.
To cut out the drywall, use a drywall saw. There are many u-tube directions you can follow for instillation. Can you do electrical wiring? as if there is no electrical, you will have to run wire to where you want the outlet.