RS2000 FUEL TANK NEEDING A CLEANOUT.

As the heading says, my buddy has just bought a car that sat in a driveway for 10 years witout being started. Took the tank out today and emptied all the old fuel out. there is a lot of gunk in there that needs to be cleaned out. the tank is like new from the outside so would like to use it if possible. Where can I get this dipped in Sydney area? Thanks in advance to anyone that can help. 
