Case / Rma / Sales Order / Job

Scenario. We sell our product that is serial number tracked, lets call it A1. Later on customer wants to send back A1 as it needs attention/service/repair. Case is raised along with Rma, Sales Order, Job. A1 comes to the site, RMA entry processed disposed to Job and disposed to Sales order. A1 goes into WIP (Status).

If we wanted to send out another unit lets call it 2A to get back to the customer due to turnaround time of 1A being too long.

What would the correct steps be in order to reflect and record this correctly?

Set up a sales order (linked to Case) to ship 2A with terms of Net 30days
When customer returns 1A (Linked to Case)
Return 1A to inventory or DMR for review.
Create a credit memo to write off the invoice for 2A.