I've gotten the elder scroll and the ohgma before doing the main quest, will that break the quest line?

What will happen when i get to the mission where i'm told to retrieve it? Is there a "oh you mean this elder scroll" dialogue moment or will they ask me to seek out a dead man?

Probably like dragon tablet fot the whiterun wizard, "oh you mean this tablet here?"

Surely someone will come along who knows, but don't read it. I think that messed up some other guy's quest - worked out eventually, but stalled it for a while.

^This.
Youll be okay.

The ohgma part isn't the main quest, it's a daedric quest. So it wouldn't be game breaking.

I've done it, there's no problems. I don't if it was deliberate or not, but there's this pause after you tell Paarthurnax you already have one before he answers. Really made me feel like I just caught this unbelievably ancient dragon completely off guard.

Don't play with the scroll too much... you will go blind.

true but the madman you deal with is so i thought him dying would mess up the MQ....i'm not saying his name because i don't want to spoil it even though this is the spoiler section

Ah, smart thinking.

Well anyways, "he who shall not be named" isn't needed anymore. So deal with him as you see fit.