Plugin update 4.0 to 4.3

I have NMI Payment plugin from Github for Nop 4.0
I need to get it running on 4.3.

I have been working thru source code and some of my questions are as follows.

Is there somewhere I can see a descriptions of changes?

Examples - in 4.0 IsGuest = _workContext.CurrentCustomer.IsGuest() works fine.
In 4.3, what took the place of .IsGuest?

In 4.0 - _workContext.CurrentCustomer.GetAttribute<string>(Constants.CustomerVaultIdKey)
In 4.3 GetAttribute is invalid.

I am trying to cross reference to other payment plugins with some success.  Not finding good examples of the two listed above?

A lot routines were changed to services
Artdtc wrote:
_customerService.IsGuest(_workContext.CurrentCustomer)

Artdtc wrote:
To get a customers first name you would do
            var firstName = _genericAttributeService.GetAttribute<string>(customer, NopCustomerDefaults.FirstNameAttribute);
So probably something similar