Hi Jim, it looks like you're off to a great start!

So for joining the sphere-ish wheels to the body, it kind of depends on how you want the join to look, do you want it to look smooth where they run into each other?

If so then the way you usually want to do that is to build the body and the wheels as separate pieces that initially just punch through each other and meet in a sharp crease. Then you select them all and use the Construct > Boolean > Union command to cut them with each other and combine them into one volume. That will then create some edges at the juncture between the wheels and the body surfaces which can then be selected and filleted to smooth out what used to be a sharp corner there.

That same technique is used in both the 6-legged pod and the sunburst video tutorials available here:
http://moi3d.com/2.0/docs/tutorials.htm
so watching those would probably help - they go step by step through the process.

If you get stuck try posting the 3DM model file of your current result.

- Michael