If i goto the tribunal expansion during the main quest (i just got out of the cavern if the incarnate and decided to go off the mainquest for awhile again) will the mainquests story be spoiled in anyways or affect my reaction to it etc?

thx

Almalexia will reference the MQ, but it doesn't effect it at all. Same with Bloodmoons.
They're all exclusive from each other.

It won't actually break the main quest in any way but it will reveal things about the storyline that may spoil the story for you depending on how far in the main quest you are

Even Almalexia considers you as the Nerevarine. There are a lot of side quests in Tribunal if you want to do them, but if you are doing a RP finish the Morrowind MQ first IMHO.