On restoring one: If it's structurally sound and has no major problems, you could just sand it a bunch, going from rough to smooth, and then give it a few coats of mineral oil, then butcher block conditioner.
If it has mild problems on the surface, you could run it through a planer first. If you don't have a planer, find a cabinet-maker or woodworker who has one -- they'd probably give it a few passes at no cost, or very little cost.
If it has bigger problems, like coming apart at a glue joint or two, it might need to be cut apart at those spots with a table saw, then reglued.
Hope that helps.