Philips 36pw9308 - bad tube? how to change?

My TV just started giving trouble. Picture narrowing in from top and bottom, some parts of the lower picture looks like it comes from the missing part on top. Small 'stripes' horisontal are also showing.
When I turn on the TV it shows normal a couple of seconds, and then the trouble starts. Within 20 - 30 seconds there are no picture left, just a small tiny stripe in the middle.

Is it the tube?

I filmed it so if anyone out here want to look at my vid., mail me and I'll send you the link.
My address is Lindstrom at gmail dott com

If it is the tube, can I purchase a new one and fit it myself? Is it expensive? Have some technical skills, but are not any tv repair guy :-)

I currently live in a country without any philips repair stores of any kind, and the few repair guys I've asked have never touched a philips TV.


Please help me solve this..