All old equipment that has been sitting will require a Clean Lube Adjust (CLA). That's part of the deal so personally I do not think it should be used as a bargaining point. If you can find one that had a recent CLA, then more power to you as that usually benefits the buyer not the seller.
With the 2.8D at hand, first look it over as well as you can. Are there any dents or scrapes? Is the leatherette intact or is it peeling off in places? Are the lenses clean and clear? Check for scratches, haze, fungus by shining a light into them. Does the shutter fire at all speeds? Do the shutter and aperture dials turn easily and smoothly? Can you easily turn the film advance crank? Does the fold up viewfinder hood function smoothly? Is the view through it clear? Does the camera focus smoothly?
If all these are to the positive, then it's worth about $800. Whether the taking lens (the bottom lens) is a Xenotar or Planar also can affect prices. People tend to like the Planar more.
Do a search on ebay, Rolleiflex 2.8D, and select the option 'sold listings'. That will give you a real idea to the current value.