Replace rr tie wall with concrete blocks

We're replacing our rotted landscape timber retaining walls and not sure where to start. There are two tiers and they are only about 30 inches high and even lower in other areas. The top tier is only about 26 inches tall. It is a fairly long wall though, about 42 feet. Should we remove the rr ties at the bottom level first and then dig, sand, level, place foundation blocks. Will the dirt stay back? Should we remove some of the dirt first and then remove the landscape timbers? Help! Not really sure how to start this project.