If you didn't want to replace the dish, it is just a standard sat LNB. You can buy it at radio shack, etc. I saw some on clearance at walmart for $10 a few weeks ago.
Getting a dish upgrade would be good to get a smaller dish, but if you do not want HD any time soon, your current situation is fine.
LNB failure is not really all that common unless something happens to it physically or electrically.