Many moons ago I bought a class 1 ballscrew from the same guy routercnc suggested and was very happy with it, still are.! Thou it did need a strip down and clean to be fair so be prepared that you may have to get slightly dirty to get best from a used components.
Still it's a good cheaper way to have profiled rails and worth the effort and risk. Even if there's a bit of play or slop then it's not difficult to replace balls in both bearings or ballscrews so they can be brought back to life or certainly far better operation.

If I remember correct they didn't take long to come roughly about 2-3wks and was packaged ok.