Good luck. This is about the least intuitive application. Need a replacement base? Sorry, they are not sold. Need someone to discuss subscriptions, good luck finding a person.
Even my original installation was a mess. Quick hint, don’t use a Google product with Apple. They have problems.
I'm surprised there are no replacement parts available. It's most likely to encourage people to move to the new products within the Google home umbrella where they push the subscription very hard. They offer little support on the subscription once you sign up. It is routinely suggested to delete, cancel subscription and resubscribe to fix the problem. Their TOS does not allow them to give prorated refunds. They also will not move your subscription to a different account or even another home you created by mistake. I do not believe their is a way to merge devices that were set up in other "homes" either. I say homes because that is what they get set up as. You can have multiple homes by mistake all at the same address each with their own subscription. Be very careful. Also there have been reports that mesh wifi can cause multiple homes to be created.