Framework image cleanup

I have a diagram that I need cleaned up and made to look suitably professional. The base diagram is already there, so the essential design is correct. However, it has been created by non-"design" people in MS Draw, etc., so it looks a bit clumsy and with many rough edges.
I want the diagram reproduced in a professional package so that it looks smooth and can be used in professional presentations, on documents and brochures, and on my company website.