The easiest method to try would be to use a program like Irfanview or Photofiltre. Just select a rectangular section of the image background that most closely matches the background color of the texted area, copy, then paste over the text. If it's not a perfect match you can play with the transparency of the paste to sort of blend it in. After 2 or 3 tries you should get it how you want. Usually with these editors if you make a bad move, hitting Control-Z backs off the last action. Just keep pasting and undoing until you get it how you want, then Save As to save to disk.