How do I change the OwnerID of a row after creating it in ContactBase with my pre-defined GUID?
--> What is your purpose of pre-defined GUID?
If you change want to change your OwnerId after creation (onCreate), there are three ways using Plugin (I use this because you said upon row creation)
1. Using code set owner id column and register your plugin as onCreate (Pre)
2. Using code AssignRequest, bust please register your plugin as onCreate (Post Create), alias postCreate Event
3. using code update owner id column with Guid from your entity.Id (current entity Id) and register your plugin as onCreate (Post Create)
I prefer to use number 2.
Thanks.