I've made a few, and then made the 3d models for them.
Diptrace kinda sucks when it comes to 3d models though. In Solidworks, you can make the part as one piece, color the faces, and then import it into .wrl that Diptrace useses, however, diptrace doesn't see the colors and it's just all grey. In Solidworks you have to create each part separate, pins, case, etc, color each part separate, then insert them all into an assembly, then save as .wrl. That's only way I've found that Diptrace sees the colors when viewing in 3D mode.
Making a part library is pretty easy. It just takes time, and patience. Just make them as you need the parts for your design.