Workflow for prompting user to pick a Case Number and Copy that incident with Contact and ORg

Summary

I am trying to put a workflow together. Need some help

Content

Hi Here is my business case

An Agent will create an incident, needs to be prompted to search for a case number and once the agent finds an incident with a case number, he can select that incident and use Copy function to create another incident with Contact and Org. Then some field like Status (will be set to open) and Details (free text custom field) will be set to certain values and the incident needs to be shown to Agent. If it is an existing incident, then it will just open the incident. If the agent does not want to make  a copy of the