If it has an impact to baselines, then it probably will go to a change control board, who will need to know all the information and impacts to the project. You need to make sure you provide all the facts and impacts, so analysing would come prior to submitting the entire change control request. Plus you will have to determine if the change request meets the criteria, if any, for the request.

In PICC, Change Request Sequnce, which comes first when asked by stakeholder to initiate a CR? Immediately submit CR or analyze impact to baselines?