A 2007 will fit a 2010
BUT you need to get all the 2007 hardware, including door surrounds.
As far as used condition, check the seams, and the condition of the windows.
To make sure it's a complete top, you need the three side and rear panels (window pieces), the upper fabric deck (the "top"), the bows and windshield header (mostly likely attached to the fabric deck), door surrounds (plastic pieces that surround your doors), a tailgate bar (might be separate or attached to rear window), and tailgate bar retainers (plastic or metal clips that hold the tailgate bar onto the Jeep).
Door surrounds are the pieces most often left behind, and they are pricey.