Those Polaroid branded HDTVs are not the best sets in the world, or so I gather from what I've read about them online. If yours is going to need more than a new inverter board, I'd just replace the entire set. I'm not sure if individual modules are repairable at the component level or not, but I'd guess not, considering they have surface-mount components and are wave-soldered by machine at the factory. That these TVs are not made by a known manufacturer (most aren't, unfortunately) is not a factor in your favor either.
I don't know how big your set is, but if it's much less than 32 inches or so I'd junk it. Smaller screen HDTVs are just not worth repairing, as the cost of repairs (added to that of the initial diagnosis) can and all too often does exceed the price of a new set.