i have the receipt and purchased the 2-year warranty. but don't have the box. should i have any problem going in and exchanging my set?

When I used to work the returns counter at a large retail chain (not walmart), when someone came in to exchange a defective TV without a box, it wasn't a problem if they were exchanging for the same model TV. Because we could keep the box and packaging from the new TV, and the customer would leave with whatever he brought in (I.E., if he came in without a box, he'd leave without a box).

If the customer was exchanging for a different model TV, then we'd charge a "restocking fee" for the missing box.

But like I said, it wasn't walmart, so you'll have to ask them what their policy is...