Over time, I've read just about every post written that dealt with M103 valve stem seal replacement.
Yes - the KD tool will work, but some will tell you it's easier to use the special set of MB tools that were around $150-$200 last time I looked. Do you REALLY need this special set for what might be a one time repair? Some have done it w/o the special set.
Anyway - here's a pointer to just about ever thread that deals with this task. In the end, you'll learn that there are all kinds of opinions about what tool to release spring pressure with and strategies in pressurizing the cylinder.
http://www.peachparts.com/shopforum/search.php?searchid=607012