VERY simple project, can't figure out the mechanic

I am a prosthetist/orthotist looking at 3d printing braces and artificial limbs. I have 3d scans of patient’s bodies that I think I need to extrude out turn into a 3d printable shell, but it gives me all sorts of trouble. I have tinkered with blender and some other 3d modeling programs for the last 3 months but still can’t come up with an eloquent solution. Is there a tool for this? I know it’s well within blender’s capabilities, it’s just outside of mine.

TL;DR: I need help printing a 1/4" thick shell for an imported stl or obj file.

This is not a job. Moved to support / modelling

This sounds like you just need to use the Solidify modifier to give thickness to the walls. Set your scene measurements to metric and you can tell it exactly how thick you want.

be sure to apply the modifier before exporting.