So I got the game, and I'm planning on downloading all the dlc's now into the game after playing for a few hours, but will any of the dlc's take away any side quests thats already in the game? Or will it only add new side quests and not get rid of side quests as of now? And also, do you think its better to download all the dlcs now, or maybe towards the end? It will be much appreciated for a reply! Thanks!

It shouldn't cause any problems with your current game to activate them now - in fact, if you want the level cap increase to 30 and the ability to play after the ending, you should probably go ahead and install Broken Steel at least.

I am pretty sure everything is good with quests. It is best to have them running from the start just to make sure that everything has loaded okay.

On 360 the Pitt dlc and Point Lookout do conflict with each and it does cause the character to fall through the roof in one part. Just unload Point Lookout to finish that part and then re-install.