+ What programs do I need for creating Sims 3 content?
You will need a copy of the TSR Worskhop 2.0 for creating any Sims 3 content. The Workshop also contains the pattern-making utility.
For other programs that you'll need, see:
What graphics programs do I need for patterns and textures?
What programs do I need for meshing and 3D modelling?
Can Milkshape read my 3D file format?