Which Dynamics version, config ourselves, pricing

Hi Jimmy-CCC 

These are all good use cases for Dynamics 365 and Power Platform.

To answer your questions,

1. Based on your broad requirements it would be worth considering Dynamics 365 Customer Service, this would provide functionality of case management, scheduling, etc. Here is a relevant customer story from Children 1st, a nonprofit in the UK, who used Customer Service and a webinar about their solution.
   While Dynamics 365 Customer Service would provide much of the functionality you require, there could be a significant amount of customisation required to suit your requirements. You could also consider creating a model-driven Power App from scratch that incorporates only the functionality you require (or incorporate relevant parts of the Nonprofit Accelerator).
2. As part of the Microsoft Nonprofit offers you can purchase discounted Dynamics 365 Customer Service, you are also entitled to 10 free licences of the Power Apps per app plan. There are no longer free licences of Dynamics 365 available.
3. You can customise Dynamics 365 and Power Apps yourself or choose a partner to assist you. Microsoft do have comprehensive learning documentation, but I wouldn't suggest building complex applications without a high level of knowledge and experience. You might be able to find expert volunteers here: Catchafire: bridging paths to stronger communities
4. A partner will generally charge for there work.

Thanks

Matt