Help! Trying to prepare model for 3D Printing!

Hello. I am a BEGINNER to sketch up and I’m trying to 3D print a head for a project (I’m making an animatronic head). Could someone please help me out by adding thickness to the parts (Thickness for ALL parts must be 0.8 cm) and fixing the errors in solid inspector so I can successfully 3D print this.
Thanks in advance,

Solid Head 4 (Head height is 20cm).skp (674.7 KB)

Side Note:
Please ignore the measurements on the side of the model in sketch up.
Please do not change the size and dimensions of the parts (length width and height).

There are applications dedicated to doing 3D printing. It would be simpler if you only did the outer shell with SketchUp, export that as STL, then use the other programs to make the model be hollow with a uniform amount of thickness. Those apps will also take care of support, and holes needed for resin to escape from, in the case of SLA printing.

See MeshMixer as an example:

I got this model off the 3d warehouse, and I also have no clue what you’re talking about.