I vic any retaining wall 1Mtr and over in height must have a building permit which means engineering comps., inspection etc. For a 3 metre high wall you will need minimum 6 metre H section steel uprights, which from memory weighs about 50 kg's per metre . This work can be done with a 5 ton excavator but much safer with a 7 or 9 tonner.
The interlocking brick system is easier but more labor intensive and can be done bit at a time once the foundation and 1st 2 or 3 courses are done.
Sorry, it's a bit far for me to have a look for you
cheers Keith