It's not that hard - starting from around Woolloomooloo, jump on Cross City Tunnel (~$2?) -> Bridge or Tunnel (free - take your pick) -> Lane Cove Tunnel ($3) -> M2 (8?) -> M7 ($8?) -> M5 (problem is toll relief on this leg) -> Eastern Distributor ($8) and you'll be back in the CBD. Or you could simply do the CCT -> bridge/tunnel -> LCT -> M2 then turn around around Pennant Hills Road doing the return leg?