I read your other thread and I'm in a similar boat. I LOVE my Nexus 5, but it hasn't received any official updates since Dec. 2016. Thank god Nexus 5 and 6 are beyond popular with xda-developers that newer OSs are available in the open source community.
I'm familiar with stock Nexus images and changing OSs off Nook, Kindle Fire, Nexus Player. Getting adb driver on a Win8/10 installed is the hardest part. Most of the time, getting the PC into safe bootup and allowing it to run 'unsigned' drivers tends to always work. Next is to display the hidden Developer settings in Android. I think you're suppose to tap the Build number 7x time to show it. Once that is running when you connect your phone via USB, ensure that you choose MTP or PTP in the developer menu. Then you it show automatically that you want to allow your laptop to debug the phone and accept it. If it doesn't show, unplug the USB, again in the developer menu remove all previous debug devices and try again.
Google's instructions off this page https://developers.google.com/android/images?hl=vi
is a concise version of what you need to do assuming everything goes well. I tend to do a full wipe since most of my apps/contacts get synched online. My SMS/MMS messages get backed up using Helium. So I tend to use the Factory images, not OTA. In fact you reminded me prep my Nexus 5 for Android O next month.
Just slightly off topic. The Google Pixel is currently on a ridiculous sale direct from Google. $524 with a VR Daydream for free. I plan on selling the DayDream for $60 knocking my new phone price to about $465. Not bad for a flagship phone.