Anyone know how to 'spruce up' a couch?

We are moving next month and have to buy a ton of new furniture for our new house.. so I wanted to keep our current couch to save money but its starting to look a little ragged.

Anyone know how to go about restuffing the cushions to give them more life? How about preventing sagging from the cushions being on top of a sofabed?

My mother had that problem, and they bought a piece of ply wood. You wopuld never know the cushions were sagging. My brother measured the couch, had it cut, and voila .