Hi Skwerm, you're going in the right direction. Often times for making a little inset piece it can be easiest to actually cut your main surface to get a smaller surface fragment, and then either extrude or shell that smaller surface fragment into the inset piece. That way you generate an inset piece where the inside part follows along the same contour as the outside surface.

See this previous post for an example:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3024.4

Also check out here for some ideas on cutting grooves into things:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3859.2


I'll try to show you some steps with your actual model in a bit.

- Michael