Normally you just go online to the nelsonperformance.com website and fill out the form and pay for the tune. They tune a PCM they have in stock with your base tune and then do the tune update to the replacement PCM. Next they send it to you via UPS and you put it in your truck. Drive it around a week and be sure you're happy with it and then send back your original core. If you keep your original PCM it will cost you the price of the core to keep it. Zero downtime.