You don't have a choice especially if they are willing to replace it. Instead, just document your conversation and the duration which you do not have the vehicle. If the issues persists, then you can go the lemon law route but it was extremely time consuming and draining. I would expect the DU to be replaced and it'll be as good as new. You can see if they will offer some form of compensation (free supercharger miles). The manager may be able to do something.