After you finish the process, you must go back and repeat the process as many times as needed. In every iteration, a new component is modernized and you are closer to your goals.
Not all the phases require the same amount of effort in every iteration. At the beginning, you probably must invest more effort in the preparation and experimentation phases. However, as the project advances, these phases are shorter. You see how the phases adapt during the successive iterations.
Evaluate your progress in every iteration and adjust your path accordingly. While going through all the phases, adhere to the principles of modernization and adjust the process to your situation.