It's a five gallon keg, pretty standard. The Challenger VI is a common keg, I don't know anything in specific about that model that would be an issue. Most kegs are pretty much the same.
I would buy a seal kit for it and perhaps new poppets if they look poor. Should run less than 10 bucks or so from any number of online homebrew stores.
I would clean it very well with either PBW or Oxiclean and sanitize it. I would also wash the hell of the outside of the keg. Provided it isn't badly dented or the lid isn't damaged, it should be good.
Gedvondur