James, It would be very easy to trace the model as you already have all of the sizes. Once you use PluSpec you will see why, basically PlusSPec automates the layers, the styles, the scenes and organises your model. Basic Sketchup geometry is just lines with no intelligence other than a 3d representation and a texture if you have added one. In saying this it depends what you want to do with the model, if you just want to create elevations PlusSpec will create elevations & 2d plans from a standards Sketchup model. Tip use the scene tool.
If you want to use PlusSpec to generate a bill of materials or a cut list you will need to redraw.