This is a BIG and expensive project! We have several retaining walls on our property that need to be redone. The photo below shows just one of the walls that is falling down (we are looking at the lower wall, light green wood).
We decided to tackle these walls one section at a time, as money and time allow. If you are looking for a way to build/replace retaining walls, doing this yourself will take time and muscle, but save you thousands of dollars. (By the way, the fenced in "boxes" up above are our raised garden beds. We live in a forest and the removable fence panels keep the deer and critters out beautifully!)