Considering the way the N9 is built, you will need to remove the screen first and possibly lift out the mainboard to do any sort of repair.
I wouldn't consider this "nearly complete disassembly", and if you want to continue using a 10yo phone you better get used to it.
I did it several times even without the special tools (but have a hard guitar plectrum or something similar handy).
In other words, I do recommend it.

If the plastic cover of the power switch is broken you can tinker with it and hopefully fix it, but I wouldn't start messing around on the board itself.

Nokia provided its customers with excellent hardware documentation, I have uploaded what I have here.