Thanks for those links! I will go through them carefully. Doing a startup is what I want to do but before any of that I want to do the due diligence part first and learn things.
The first half is run of the mill startupy stuff, but the second half has a lot of useful information to consider.
I'm not sure how helpful the blog links will be at this point.
Re: External Casing- If you have access to a 3D printer, I highly recommend trying out a few iterations of the casing yourself before you try to outsource.
Once you have everything working, you can find companies that do limited runs of PCB and casing.