Chosen Solution

I broke the microphone assembly ribbon cable, from step twenty five. Is there anyway to fix this, soldering kit, or can I order a new cable online?

You’er in luck! Here’s the needed cable MacBook Retina 12" Audio Board Flex Cable If you damaged the speaker cable you’ll need to replace the full speaker. Update (07/12/2019) Read Fuller - I was a bit perplexed as Step 25 deals with two cables. If you had pointed to Step 17 in this guide it would have be clearer Retina MacBook 2015 Audio Jack Board Replacement and here’s that cable MacBook 12" Retina (Early 2015-2017) Audio Board Flex Cable