I don't think there are too many 50" flat panels around $300 and if there was, I surely wouldn't want one.
Given the fact you are light years ahead of 95% that post here by having the service manual and actually knowing what you are reading, without knowing the prices for those boards, the technology of LCD RPTV's was never that great in the 1st place. I wouldn't really bother with it. But that's just me, especially if this is your main TV.
BUT, if this is something for a spare room or basement, try reseating all the connectors and start shopping for those boards.
Abundant OTA television is what makes this country different from all others. Lets keep it this way. If you like Wi-Fi so much, OTA fits right in. After all, it is wireless.