Maintenance on 14 C Two with 188k miles

Hello all! I have purchased a Prius C from a salvage yard, unknown history or repairs. Not a great idea, but not quite as terrible as the pervasive stench of combined wet dog and cigarettes.
As I tear into the front radiator supports and body panels, what maintenance should I keep in mind and/or do prior to putting everything back together and making my life difficult down the road? Planning on changing fluids and such, plugs etc.

Also, for some reason, car started doing this odd noise today when moving from a stop, sounds almost like a really cheap Chinese camera's boot up sound from 2006. Not sure what this may be, if it's still present when I get around to it, I'll try to upload a clip of the sound.

Thanks for all of your help, everyone, and happy to be part of the community!

 

Here's a video of the sound, for anyone that cares!

 

fascinating, thank you! previous owner must have unplugged it at some point and then I accidentally plugged it back in when screwing about with the front end haha.