I found this to be helpfull and informitive, hope it can be of use.
Special Tutorial on Hybrid Modeling: This update guide has a special
tutorial that utilizes the hybrid surface-solid modeling approach of
Autodesk Inventor 7
· Detailed explanation of inserting AutoCAD 2004 file in the sketching
environment of Autodesk Inventor 7 and how to open a Mechanical Desktop
2004 parametric model with features in Autodesk Inventor 7