Not for $100, sorry. Not even used, broken, and left out in the rain for $100 The first step would be to calibrate your monitor. Windows has a tool that does this decently in the control panel.
When you say they look over exposed, do you mean when you print them? Or they look fine on the camera but over-exposed when you get them to the PC? Your cameras LCD is not a calibrated display. It's 'for reference only', so to speak. It's possible they look good in your camera, but don't look good when they get to your PC. If you are printing images at home, your printer will need to be calibrated as well. Google 'using the histogram' and learn to use your cameras metering tools to judge exposure, not the preview images.
So again, first step- calibrate the monitor. Calibrate it monthly, and calibrate it any time the light changes (replace light bulbs in the room, etc.) Also, calibrate it with the blinds closed and do your editing with the blinds closed. Changing the light can change how they look.
If you want to get serious about photo editing, then you'll need a color accurate IPS display. These will START at about $1,000. There are a FEW bargain basement cheapies for $500. The problem is, cheaper LCD displays are TN displays, not IPS displays, and they cannot reproduce all of the colors in your image, often making them flat or washed out, and inaccurate. Then, when they get to a calibrated printer, or someone elses monitor, they look awful!
Good luck.