The tube will cost round 200- 500.
rest you can find it from the mechanic who is going to repair it,
or you can also find out from the spare part shops.
I dont think it will be covered under warranty.
Most of them do not cover it.It will cost you more to have it repaired than just buying a new one.
The labor cost of repair is very high.
You will notice that Panasonic has a tv recommended in each price category of entry level to the high end.
Sony and Toshiba (the top other brands)
Other brands like LG,
Sanyo and Vizio (the next 4 brands)
did not even get mentioned.
The cost of LCD screen is really very high and costly.