Introduction to 3D in XNA

For my next XNA project I think I should move into 3D. The Spacewars starter kit still looks complicated but I think I've come up with a game idea that can make use of 3D while still being relatively simple to visualise.

I'm not certain of this idea so won't go into detail yet, but I will need to figure out how to place models in the world and move the camera for any 3D game to work.

I've found an introduction to 3D models in XNA, and an introduction to matrices that should help somewhat. I've managed to render one of the Spacewars models into the game and can move the camera around in the way that I want.

Now I need to get the model moving based on mouse input. Oh, and get some 3D models to display in the actual game. I've found Turbo Squid, but what I've found on there can't be imported into XNA and need to be opened in 3D modelling software, which I don't have.

Does anyone have any recommendations as to some free software I can use that will let me create my own 3D models?