Definitely taking longer than expected, but I am making progress...albeit haltingly.
I've a long way to go before I'm familiar with Sketchup's full capabilities. Sometimes it seems like I'm making good progress then I hit a stumbling block and I have to rethink how I'm doing something and how I can best proceed. The Contour part of the Sandbox Tool is helpful, but it isn't my preferred way of doing things because it still requires a contour of lines to get the shape you want. I prefer manipulating shapes where possible to get what I want. Although I've only experimented with the standard colours and textures supplied it's nice to know that I can import others better suited to my purposes. That said I'm not ready to start colouring things yet. Presently I'm just trying to get the entire main hull of the scoutship together and then the other components before I think about colour and textures. In the end, though, I do want the ship to have something of a metallic or alloy look to it. I envision the overall colour to be a very light grey similar to what we saw on the TOS shuttlecraft. I'm thinking of making the nacelles a bit darker grey with red (similar to the that on the 1st pilot Enterprise)
or perhaps even white nacelle domes. The forward viewport I see as a dark blue or smoke tinted that you can't really see through from the outside as it's meant to be a one-way transparency.
Although I'm confident I'll figure how to get the whole model done I am mindful of the aft end nacelle cowls and their distinctive curved shape and corrugated surface. I can think of how it might be done (with the Solid tools perhaps), but it remains to be seen.