As long as you didn't open the xbox, your warranty lasts 3 years. If you opened it or modded it your xbox warranty goes void.
If your warranty is actually out, you can search e74 permanent error fix on youtube and find quite a few movies showing you what to do.
Sounds like something skin makers have been over looking. Almost every skin I've installed the numberlist doesn't work.
If you end up figuring out how to fix it, i'd appreciate if you sent me a pm how to do it.
I would like to use this feature on all my skins too :P