Hi Shira - we recently started using Arrows to help with this. Our need is more focused on initial onboarding milestones (vs year 1 milestones), but it allows you to set due dates and then sends automatic reminders to internal and client stakeholders to complete tasks (ie update the running note document). You can also include a link to the google doc as well. Other thought is that if you have an existing CRM, you could just set up auto-reminders based on the Contract Signed date to the account owner to check in with the customer / update the document / etc on 30 days post contract sign date, 60 days, etc.
Hope this helps!