I learned how to operate on a crane similar to that one a few years ago, and it wasn't the easiest to learn on. I'd much rather have learned on the National 1400 that i'm running now. You should definitely think about hiring a seasoned operator to show you the ropes for a season or two.
It doesn't seem like the greatest deal for the $$. My old company just bought a newer ('96 or '97) 40 ton grove for about 15k less than the asking price on this Krupp.
Also, its been owned by a tree service, and theres not many tree company crane operators on machines of that size who stay strictly in the confines of the load charts and never cheat a pick, potentially sideloading or shockloading the boom. Spend a couple hundred and get a reputable, knowledgeable company to do an inpsection before you dish out that much cash.