What 1880snonsports said is all true. As opposed to cards, posters, photos and some other ephemera can actually have their value enhanced with conservation and/or restoration. I too am a minimalist in this area and try to keep my items as close to original as possible. I know the quite expensive Horner Composite photo I have has had conservation and a tiny, tiny bit of restoration work done to it. I am fine with it. I have the paper saying what was done and it was mostly cleaning and deacidifying the paper (I believe, it was done before I got it)... Here is the company that did it. They are good, many auction houses and collectors use them, but they aren't cheap...
http://graphicconservation.com/
Good luck!!