I'm sure you will be fine. When I brought mine in, I kept dropping hints that I would prefer an LG, but of course, I didn't expect anyone to actually write that down. I brought my laptop in to my nearest apple retail store so the genius could look at it. He then had me sign the repair order and said he would mail it off to be repaired. I had the option of having it mailed back to my house when finished or picking it back up.
I chose to pick it back up as I expected another Samsung screen/lots of scratches. In the end I got lucky. If you do receive another Samsung screen, just raise hell. My advice, however, is to look for yellowing before you rush to see who manufactured your display. Don't forget, there are still users on the forums who have yellow LG screens.
In my case, I always expected the worse and was pleasantly surprised when things worked out. It all depends on who you speak to and your general attitude. Also, I recommend you check your repair status often (
www.apple.com/support then click "check my repair status" on the lower right).
Also, make sure you have everything backed up before you send it off for repair (they will make you sign a wavier saying everything is backed up).
I also recommend setting your background to gray and autohiding the dock. This makes it easier to see the yellow. In my case, the genius moved a finder window from the top to the bottom and noticed it right away.