ok.
I am probably nowhere near completing the main quest of this game, but I've done my research on DLC I'm still a little confused:

1) In any of the DLC, do you start off with level, items, or other experience carried over from the main quest in capitol wasteland, or is it like
a whole new game where you start off with absolutely nothing (level 1)?

2) Are DLC maps accessible through geographical points in the capitol wasteland map? Or are they completely independent of the main
quest in that they are accessible, say.. from the main menu of Fallout 3?

3) I've heard that Broken Steel is different than other DLC because it's supposed to be some kind of extension to final part of the main
quest, and so it's not really like the other maps for a couple of different structural reasons. I've also heard you are not supposed to
finish the main quest before downloading Broken Steel for the same reasons. If this is true, then how would a noob know not to
complete the main quest before they downloaded Broken Steel? (no spoilers please!)

1) You always start the DLC with the same level as you had in the CW. In the Pitt, Operation: Anchorage, and Mothership Zeta your stuff is taken from you but you will get it back before returning to the CW.

2) They are all accessed in game with new locations or altered locations.

3) I've never had an issue downloading Broken Steel before finishing the main quest minus a time when Three Dog spoiled the ending of the game with his radio broadcast.

"1) You always start the DLC with the same level as you had in the CW. In the Pitt, Operation: Anchorage, and Mothership Zeta your stuff is taken from you but you will get it back before returning to the CW."
thanks! clear enough!

"2) They are all accessed in game with new locations or altered locations."
ok good, sounds like what i was hoping for.

"3) I've never had an issue downloading Broken Steel before finishing the main quest minus a time when Three Dog spoiled the ending of the game with his radio broadcast."
Nice, I'll be sure to ignore Three Dog, then. But I didn't refer to possible issues downloading and playing Broken Steel before finishing the main quest, I referred to possible issues appearing after finising the main quest. And would that be a possible issue for any other member of the DLC lineup?

I heard that I would have to restart my game. Is this true?

i hope not. lol

P.S.***
I forgot to mention in my original post that this is on XBox360. Sometimes these things make a difference.

No, it's not true. Broken Steel plays in, after the main end-quest, "Take It Back". Once you've completed that quest, you will go into a series of Broken Steel quests, until you reach the Broken Steel end-quest, "Who Dares Wins". After that, you can keep exploring the wastes, as Broken Steel gives you neverending free-roam and boosts level-cap to 30.

word up