For scanning you can try and do it in pieces, some scanners will allow you to do it in a few different pieces and then merge them together. You could also find the software to do the same thing. It may not come out perfect, but it would be better then nothing.
To preserve it you would want a piece of plastic sheeting that is acid free. You can find them on the internet and such at places like Gaylord. It will be expensive for one item, but it will at least preserve it better then it is now. You might also want to talk to the archivist at the local historical society or library.