I live just outside of Canberra atm. I still have the 4000 motherboard in storage, I removed it from its case and pulled the RAM from it. I noticed the battery starting to leak a few years ago and carefully removed it, cleaned the board and and soldered a replacement on it, it all seemed fine but then one day it refused to boot up and after opening the case and inspecting it I noticed some corrosion on the circuit traces near the new battery, I guess I didn't clean it up as well as I'd thought or didn't get to it in time.
Well, i will leave you to decide what to do with the motherboard, but if its decided you want to "Dispose of it" i will pay for it to be disposed of to Melbourne..

I suppose it all depends on how much its going to cost you to fix it up (if its able to be). The "Gunk" sits underneath the chips and they have to be removed to clean it up...
either Iso (Isopropyl) or Baking soda paste (with water) as it neutralizes the acidity. I personally like to just flood (Yes literally FLOOD) the area with ISO because of its evaporation rate.