Do it yourself

Hi folks! I just joined the group and had my own question about door warpage. My house is a small cottage built in 1927 with almost everything original except the paint. I've recently begun some projects to update things: replacing the knob & tube electrical, the brittle plaster in favor of sheetrock, and the blown-in insulation in favor of something that actually insulates. I noticed while working on my den (2nd bedroom) that the door is warped. A little checking shows the frame is plumb & square, and removing the door for painting verified it IS the door that's warped. The curve is more pronounced at the top of the door, about 1" off centerline. The bottom is only about 1/8" off, both in the same direction. I'd really like to keep the original doors (mainly because new ones like it are REALLY expensive). Does anyone have any tips on how to straighten them? Thanks! Rob ps. I only have basic power tools (circular, drill, jigsaw, sawzall, & router), so depending on how complicated the solution is, I might just end up living with them until I win the lottery. ;)