There are several levels of Documentum certification available. The first (Associate) requires the Technical Fundamentals course. After that you can specialise as an Architect, System Administrator and Developer.
All the learning paths (and associated certification details) are available here: http://mylearn.emc.com/portals/home/ml.cfm?actionID=29&lp=ecm
Let me know what other information you need.
Technical Fundamentals is the certification level you want. There is a corresponding course. All other certification levels are more appropriate for technical staff (developers, architects, and admins).
As an add-on, you may wish to take the "Documentum: Planning, Readiness & Deployment" course, which is a 2-day course.
As as general rule, there can be a fair amount of coding during the implementation of a Documentum project. Any PM courses in managing development projects will help you as well.