Looks like you are rather new on this forum, so I am going to be nice. When you ask for help, you REALLY need to give us enough information to allow us to be ABLE to help you. For instance, how bad is the damage (PICTURES)? There is a BIG difference between a few small rust spots and serious cancer that includes the inner braces. Next, do you have the skills and equipment necessary to do your own work, or will you be paying someone else to do the work? Pictures are VERY important when asking questions like this. We see this all the time, and we can't help with incomplete information.
That being said, If you CAN do it yourself, and if the damage is NOT to severe, I would definitely repair your current fenders. If you have to pay someone else, the used fenders might be a good choice. However, if you do decide to buy used fenders, either insist on lots of pictures, or go look at them.