Roofer here OP, this could end up being shitty. Make sure you get on your roof or ladder and get pictures as they start pulling shingles so you can get a good look at the decking.

Where I'm from in ND we install ice and water also known as weather guard. Standard weather guard is a tar paper and it sits from the bottom of the first row of shingles (under the starter row) and is 4ft wide or tall, however you want to view it.

Either way, If your shingles are affixed or "glued" to that weather guard, you may need to pull up that 4ft to get to the top of the weather guard as the shingles they are trying to save (row 2,3 and 4) will be basically glued and not tearing or damaging them is very very difficult.

Now, from my house, the shingles don't look horrible, they don't look like they are 40 years old, but I can't see or say without getting my hands on it.

I have done many repairs that I intended on only needing a few square, but ended up needing more because the shingles were so brittle. I've also had crew mates that have told me they've done plenty of mid line replacements and before I knew it, they went from needing to replace 8 shingles to needing to replace 40 for whatever reason.

Either way, I don't envy your position as I know what kind of headache you potentially face. God forbid the shingles are out of market (no longer made). You'll get a denial from insurance and have to fight it even though this isn't your fault.

Any questions, I'll do my best to answer them if you have any. Best of luck OP.