I found the PDF for what I think is your system. Here is a
Link to it. It looks like you use the Input Setup Menu to change the image setting. Not a lot of words in the manual but on the Input Setup Menu you will see the word mirror. Changing that setting from what is now to the opposite should reverse the image. To get to the Input Setup Menu you press the Menu button and then use the up and down keys to highlight Input Setup then press Select to enter the setup menu. You use the + - volume keys to cycle through the choses for each input (ON Normal, On Mirror, Off) once you have each input set correctly press the Menu key to return to the main menu.