I know the community levels carry over, so my assumption is the first LBP levels would be my only loss if I traded it in? 
 
Let me know guys, and thanks in advance!

Yeah, the LBP1 story levels would be your only loss. All of your unlocked costumes and stickers carry over to 2. All user made levels carry over like you stated, and so does any DLC you purchased. 

It depends, a good percentage of the costumes are locked out for LBP1...so you need LBP1 if you want all the outfits.

" It depends, a good percentage of the costumes are locked out for LBP1...so you need LBP1 if you want all the outfits. "

It's worth whatever you're losing. LBP2 is just plain better. 
 
Sure you lose the first game's story mode, but I didn't play that the first time around. 

I would say keep LBP1. What is it going for at Gamestop? $17.99? I don't know, for some reason the game doesn't show up on their site. Anyways, they'll probably give you $2-5 for it. So just keep it as a collectors item.

If you didn't get all of the items from the first then it is still totally worthwhile to have.  I'm sure trading it in will be a waste as game stores will probably take it for less seeing as 2 is out and everyone will get that.  I'd keep it just incase you want to go back and ace the story levels.

It sorta is, but theres still story missions and story unlockables