Do lots of research online (I agree with SirFelixCat about www.avsforum.com
), then go to the store and look at the sets and their pictures. Then buy it online.
You'll most likely get it a lot cheaper, and hopefully pay no tax or shipping. And I agree with others...I wouldn't recommend taking out a loan to get a TV. When you're done paying for the van, keep setting that payment aside and you'll be able to pay cash for a new TV just a few months.
You didn't mention HD, but if you get an HD set, make sure you get HD programming. It seems as though standard definition programming looks worse on an HD set, but it can vary by television, I'm sure.
I can recommend the Sony SXRD sets. Awesome picture.