50" HD plasma… hmm… not the easiest television to disassemble and repair.
My best advice is to get it to a qualified tv repair shop, get a price estimate, get a no-cure-no-pay agreement and get some warranty period (three months or something). It will cost ya some money, but better to have a decent repair than get lots of problems with your device forever.
Other thing: If they think it is a capacitor, then why is this not covered by the factory warranty? Seems the guy has seen a lot of capacitor problems with this model? Ask some more!