Thanks everyone. Since Dave originally said he did not see anything wrong with the sample model then I assumed that my Sketchup 7 is also if not entirely to blame, so I removed the skp file. I eventually isolated the places that were generating problems and remade most of the model from scratch.

What you plan to do with the model makes a difference too. You may want all the components as solids so you can print them individually, therefore needing the joining faces, or if you want to explode everything into one big solid when you have finished modelling, then removing the joins is helpful.
With a large variety of possible software and usage I don't think there is one best option.

these are fabulous! glorious detail!

The pro version can export the files you're after directly.

Amazing, I like it!

impressive model !