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If you want to get an idea about how they render, I used the 55/3.5 the week ending February 5 and the 105/4 the week ending April 23 on my D700 and the w/e March 19 on my D300 in the One week... minichallenges.
For autofocus to work with those lenses you need a body with an AF motor in the body. The D7xxx series are the cheapest relatively modern bodies that do so. Some old Sigma lenses don't work with modern bodies as the communication protocol Sigma reverse-engineered wasn't complete. Why not start by getting a battery and a roll of film for the N6006, shoot some and have the film scanned by the lab? Then you will know if the lenses work at all.
One nice thing you get by going with the D7000 is the ability to meter the light with Ai and Ais manual focus lenses. This lets you use the cheap and *very* sharp 55/3.5 and 105/4 MicroNikkors.