is the DP600 an all bearing machine? Problem with drill presses that old (and machinery in general) is that they usually have bronze bushings in some places, making maintenance much more complicated (sealed bearings are just a superior technology). That alone would make me to think twice before getting one (I learned my lesson after getting a full size, worn out, plain bearing, flat belt lathe).
If you insist in getting this particular machine up and running, I'd suggest you to consider what a machine with similar capabilities would cost today. I don't remember how much I paid for my Jet 20" drill press but I think it was around $1,200. And I don't think it is as rigid as a DP600 (I could be wrong).
What I'm trying to say is: don't cheap out on your project. It's like with cars: it doesn't matter how much it costs second hand, to repair will always cost as new. However, unlike an old car, a refurbished drill press will probably give you full service because such machines haven't really changed in a long time. Or more accurately, they've changed... for worse.