A back-bar cooler is a perfect ( and intended) use for these larger machines, in so far as he compressor question, yes, a modern replacement (the compressor deck assy.) will adapt quite nicely into this machine if it should need one now or down the road.
pricing; I'd offer $200-300 for such a large 3-door machine, less if it's not an embossed model like this one ( WH23D), & especially less if the sliding tops are dented ( way less!) because even in a back-bar insatlation as you have planed, it still has to look nice. & i'd make sure it has it's vertical dividers & bottom spacers ( the bottom spacers form part of the return air path for the cooling system, without them, the far-end of the cooler will run much warmer than the near/evaporator end)
Good luck & I hope it's on ground level for you ( I wouldn't want to huff it up a set of cellar stairs)
