I believe it differs from state to state. Here in Vic i think it's 6 months but I'm not sure. A quick search at your state wildlife authority's website should give you the answer.
Um, depends on what it is. If it's a cracker RHD or Uluru woma or something like a Platinum mac or a nice richly coloured Wheatbelt stimmy, you'll have no trouble finding a buyer. But if it's something much more common like say a carpet or a childrens or a normal mac, then I'd agree, it'll take a while to sell