I took in a 500cm with 80mm Planar as a trade. Mine came with both the original screen and a Beattie Intenscreen. I also highly recommend purchasing one of the bright screens available.
The 80mm is nice and well balanced but an old design. If you want the sharpest you need to buy the latest Zeiss computer designed lenses. Of course they will be pricier.
If you plan on using long lenses you might prefer a later model than the 500cm. They have gliding mirrors and do not vignette like the 500cm does.
KEH is an excellent place to buy. On numerous occasions when pricing Hasselblad lenses I have actually seen KEH less expensive than ended Ebay auctions. I would check KEH first before bidding on Ebay. I'm not saying to not buy off Ebay but to go into it educated before you make your purchase. Hasselblad cameras and lenses are not cheap!