As par your requirement to convert both .dwg and .prt files to CGM, I think we need a long term partnership in your projects.
I am a Mechanical Design Engineer in a reputed multinational CAD firm. We basically do Design, 3D Modeling, 2D Detailing, CAD Translation, Conversion & Validation.
If you provide sample .dwg file, my converted CGM file will assure you that the quality and time meet your satisfaction.