1975 Norton Commando 850 MK3 - newbie - how to start?

Hello. Have never joined a forum before but super excited to join this forum.
I have recently been gifted a 1975 Norton Commando 850 MK3.
This motorcycle has been sitting in a garage in Oakland, California since 1996 (last year of registration).
It appears this was the original owner.
It's non-functioning, rusty and generally in bad shape.
I thought it was beautiful on first sight and my OCD couldn't stop spiraling.
I don't have much experience with motorcycles, but I am very excited to learn.
I have some experience with automotive work and I am mechanically inclined so I believe I can do this, slowly.
I've read through the original owner's manual a couple times and I'm working on a task list and items I'll need.
I'm in no rush: if this takes a few years that's fine by me.
Also, I believe (famous last words) I have the resources to take this on.

My question:
Where do I start? The key doesn't even fit in the ignition (both rusty).
Should I just spend a week or two trying to remove rust and corrosion so I can see it clearly?
Buy a battery to see if anything turns on?
Replace all fluids immediately?
Any recommendations for reference books or learning sources would be greatly appreciated.
Thanks so much for any help.

Congrats,
Got any pictures?
That will help on where to start?

The Norton Commando Restoration Manual by Norman White is a good place to begin.

30 years is a long time to sit and if it’s corroded that badly on the outside the insides are likely all stuck too. It’s probable you will at least need new pistons and rings and an overbore.

Fortunately, there are lots of good parts sources out there. In this forum you will soon become very good friends with Greg Marsh.

Welcome to the forum and Norton ownership. There are a good number of Commando specific service/restoration videos on YouTube....Jesse's Vintage Garage has two or three Commando restoration series for example. Your bike will be positive earth, be sure to understand what that means before doing any electrical stuff or connecting a battery.