1. Just arrived at a city where I was approached by the DG. My question is: does this start the DLC and later I'll get the chance to be a vampire lord or is this part of the choice? This guy is the first of the DLC that I've encountered so I guess I'm asking if once I choose with this guy asking me...am I set on that path?

2. Will becoming a vampire lord prohibit any of the vanilla questlines (besides Champions....already did it.)?

1. You have to join the Dawnguard first to get the quest that gives you the choice of becoming a Vampire Lord.
2. No, the only quest you miss out on is the Dawnguard side.

ty ty