I had the same sitiation you did. I needed a retaining wall about 100 ft long and 4 ft at the highpoint. It cost about $6,000 using EP Henry Coventry stone. I could have saved half by putting the wall in myself but I was occupied installing 300 linear feet of aluminum fencing that took me a month of weekends. We put in a 16X32 kidney but I wish it was a 18X36.