[2022] Warlords of new york

So, it says that if I start warlords of new york expansion, I will jump to level 30 and skip the main campaign as a whole. That means that if I go to New york and complete the expansion and then come back to DC, I will no longer be able to experience the fall of DC (Correct if I am wrong). My question is if before completing the main campaign as a whole, I reach level 30 ( I am level 25 right now with 3 more zones to unlock) and go to New York, will the main campaign missions which I did not play still be skipped? If they will be skipped, will I get their rewards? What about the classified missions, will those also be skipped?