If I were you I'd take the TV back but there are some options that will work for you if you don't want to do that.
The quickest answer is that you need an HDMI switch. Does it need to be HDCP compliant? Accell has a
2-port HDMI switch that is HDCP compliant and comes with a remote control. It's probably the cheapest switch available for your particular problem.
You could also use an HDMI adapter to switch either your HD receiver or DVD player to a different type of input. We have pretty inexpensive solutions for that.
HDMI to DVI Adapter - This is the best option because it keeps the signal digital and so you can expect little to no loss in quality but then you need something to handle audio. If you can run a separate audio line from your equipement outside of the HDMI this is a pretty cheap solution.
More advanced solutions would be something like the
DVDO iScan VP20 HDMI switch this is a lot more advanced and probably overkill for your problem. It handles three HDMI inputs with a single output and provides advanced resolution/display control along with numerous audio inputs and automation options.
If I were you and I had separate audio lines that I could use I would use the second solution (assuming you have DVI input on your TV) otherwise I'd go with the first solution.
Hope that helps.