Return it. Face ID is a critical feature. Could lead to front camera problems too. Also means no Apple Pay. If you ever want to trade it in, it would fail diagnostics and you might not be able to.

What happens to Apple Card monthly installments if the Apple Card goes away?

1. Data is safe

2. No need to change passwords, but it would be good practice.

3. Never remove it from find my, which is different than removing it from iCloud devices.

4. You’re not getting the phone back.

Assuming they can’t turn off find my using various methods, you’ll be spammed threats, likely progressing to death threats, regarding giving up your Apple ID. Ignore them. It’ll be scrapped for parts.

Lesson learned, make backups.