Panasonic CT27HL14J failing after one hour

In 05/04, I purchased a Panasonic CT-27HL14J from a known retailer. Approximately one hear later the pictures seem less then clear. Just as I pay off the $600 same as cash deal, the television starts to display the following problems.

1) there is a high pitched sound emitting from the set after about one hour.

2) When the stations are changed, the picture does not change.

3) The volume will not go up or down when the volume control is used.

4) Sometimes turning off the set, and turning it back on will fix the sound, but not the picture not changing.

5) Eventually, after two or three hours of use, the picture will turn black on all channels. I was using the VCR and DVD players to watch movies when this happened, but now the movies will not show up on the television.

I have ruled out the antenna being the problem. My gut tells me it could be the tuner, but I am not certain.

Does anyone have any ideas on how to diagnose further, and repair this.

THanks, Rookie.