I've just installed Blender and i'm overwhelmed how advance the interface and the layout is compared to Milkshape and I don't how to get started. Is there any good tutorials out there for Blender users? Also where could I find 3d models of the sims' bodies?

Not sure if it will help you but you could try looking on the sims 4 studio site. There are a few tutorials there and if you ignore the studio bits they give a fair bit of information on blender. Sorry I can't help with the models.
Hope this helps.
Scottiedoag

Bodies can be found here: http://modthesims.info/t/411795

any tutorials on meshing, I'd recommend starting here with the basics and from there you'll find yourself kind of training yourself on meshes. What also helps (after knowing the basics of course! ) is to follow specific 'let's make this with blender!' tutorials, which there are plenty on youtube, thus easy to find

Here's the series I started with: https://cgcookie.com/course/blender-basics/
I also really loved playing around with these: https://cloud.blender.org/courses

Thanks.