I would estamate 45 hours of my time (not including the machine shop time). This is a different animal when it comes to dissecting the 116. I have a fair amount of mechanical abilities, but MB engineered this engine to last and working on is not as straight foreword as a American engine. Different tools and different fastners, clamps, and the (NM's) for torque. It is much easier and less time consuming with a service manual, but the biggest help is without a doubt the first hand help from fellows like my local tech. this website, and interested friends like you. I do have a new appreciation for the MB techs. As a group they are some of the most professional mechanics I have had the pleasure to deal with. Also Mercedes has been very reasonable to deal with. I live close to Newport News, Va. and "Tysinger Mercedes" is my local dealer who I will always be a faithfull customer and would recomend to anyone in this area with MB problems. I enjoyed the experience and will continue to mantain my 420 and expect many more miles out of it.
My MB runs better today than it did when I bought it. Thanks to everyone who submitted a thread to my questions....