Retaining wall plus terrace steps - how do I find out how it was build

Our house has terrace steps at the back that go up to the neighbour's house (the garden section of the original property) the neighbour is on the hill, we are at the bottom.

I want to take out 1 terrace step to create a flat garden but don't know if there is a retaining wall or not. The terrace steps are made from cinder blocks and they are hollow and no reinforcing.

I don't know if the terrace steps are creating a "weight gusset" (if you know what I mean) to support the retaining wall.

The house is build in the 1950 (state house) but I can't find any info on my maps and when I asked my neighbour if she had any maps on her side she instantly said she will deny any work done as she doesn't want her concrete parking area to Crack. She did give me her plans though and it says on her plans that there is a retaining wall.

After all that long explanation, is there a department I can go to to find this info out or must I bite the bullet and get a geo technical engineer out to assess it?

Cheers