1) Arapiles/Grampians are the best, and are close together so you should visit both. In your grades the Trad climbing is the real attraction but there are decent sport climbs in the Grampians at those grades too. Nowra is not worth it for tourists, as it's not very attactive and the climbing in the lower grades is average. Point Perpendicular, in Jervis Bay close to Sydney, is much better. It offers beautiful sport and trad climbing on sea cliffs. Go there instead.
2) One sixty meter rope is enough for most routes, but doubles can be useful for abseils occasionally.
3) Guidebooks: http://www.pointperp.com/index.html http://rockmaster.com.au/index.php/select-vic http://osp.com.au/?cat=10