The buyer of my home has asked we replace a large reataining wall. It is rotted and does need replacement. Our home sits below street grade, and we installed a beautiful entry stairway with the interlocking pink walls. This ends at the porch entry of the house. The wall needing replacement meets the new pink wall as it curves around the house. The rotted wall is straight, across the back of the house (about 6 ft from house). It sits on a dirt 'shelf' where there is ivy, a rodedendren, and an evergreen tree that's not too big. All the plants can be torn out. The wall is about 4' tall, maybe a little more. On the other side of the wall is lawn to the street. Under part of this lawn is the septic field for our highly upgraded septic system. I do not think the removal of the existing rotting wall will effect the system.

What is the easiest, most cost effective way to replace this wall?
Will replacing it with more ties be wise?
Does one have to prepare the base for a tie wall in the same fashion as the interlocking bricks?
We don't have much money, and we really need to sell the house. They're already getting a fabulous deal.
Thanks