You don't need one.
Anyway, I somehow recall something about warranties restarting or whatever when something is fixed. That might be me misremembering, as Roger Clemens would say, and it's not like I have time to go digging through the internets looking (although I did a single search on google to no avail). Plus we're still three months short on 3 years for the launch systems, so the existing warranty could be good for a while longer, depending on when it was built.
At any rate, it seems fixing another RROD out-of-warranty would likely put your cost up there with just buying a new system.