I've never owned a 500, but I am a lefty and I do find the page turning buttons on the 505 quite comfortable. On the 505, there are two sets of buttons you can use to turn pages with, and I find my self using both of them depending on the position I'm holding my book at.
My recommendation is to upgrade instead of paying $250 to repair--but, maybe you could stop in to a store and play around with the 505 and see if you could get used to the position of the buttons.
Good luck with your decision!
dordale
