How to fix my Plasma TV?

I have a 42" Sanyo Plasma TV, that no longer works. It has no picture or sound - it is totally black. The problem first began with half of the picture blacked out, but it had sound. Sometimes it would just fix itself, and sometimes we would need to turn off the TV for a while, and then turn it back on. I guess we were hoping that the problem would just go away and the TV would fix itself permanently (Denial, I think). That worked for a time, and then one day, I turned the TV on, and had a beautiful full picture, and then it went out; picture and sound. Would a pixel corrector DVD fix this? Just can't afford to take it to a shop at this time. This TV was quite expensive when we bought it 3 yrs ago, and for the money paid for it, it should give us years of viewing. We have a 25 yr old JC Penny, 19" TV, that STILL works. I guess, things aren't built to last these days.

Thank you to anyone who may be able to help.