Mid 2015 MacBook Pro gives me orange light, fans don't spin.

Well, its clear your logic board has a problem. This maybe a deep problem like a dead CPU or GPU chip. Its also possible its a blown power MOSFET which is an easy fix.

The issue is what is your skill set and access to the needed tools and schematics/boardview drawings to even diagnose the problem and then access the needed tools and access to the needed parts to repair it?

As you've stated you don't have the schematics/boardview drawings you'll need to do that, do you have everything else you need to fix your logic board?

Or, from a cost perspective does it make sense replacing it with either the same or better logic board for your systems series?

Or, does it make sense finding someone who can fix your system as they have whats needed.

You'll need to do the numbers to see what works for you.