Adjust .STL Design to Editable CAD Model

I need an existing .STL design adjusted and rebuilt as a fully editable CAD model in FreeCAD. The updated model must reflect specific new dimensions that I will provide.

Requirements:
- Dimensional accuracy is crucial.
- Design consists of five simple parts.
- Include clear instructions for non-CAD users on:
- How to adjust dimensions for each part.
- How to export the model as an .STL file.

Ideal Skills and Experience:
- Proficiency in FreeCAD.
- Strong attention to dimensional accuracy.
- Experience creating user-friendly adjustment guides.