If the lines are clear enough, you might run the scanned images through an application such as WinTopo to create vector lines. I believe PhotoShop could also do that. Then you could import the vector lines into SketchUp and have most of that work done. To import the vector lines, you'll want SU8 Pro or you could try one of several plugins for importing DXF files into SU. Look at the list of plugins for that.