This tutorial will show you a simple example of cloning a Sims 3 object and replacing its mesh with one created in Blender 3D. You will learn the basics of mesh replacement with Blender, including creating a mesh, unwrapping, and UV mapping.
This is for beginners. It is to be considered a introduction to using Blender for Sims 3 object creation. Although some basic Blender functionality will be covered, this is not a tutorial to teach how to use Blender. I suggest trying some of the many Blender tutorials to learn how to use Blender efficiently. I'll be more focused on using it for Sims 3.