Not to worry! I think the problem was the original head which was brand new. I understand that 1 in about 1000 will have or get a broken valve guide. It looks like this other brand new head is holding up, also we put a new PCV, oil sensor, oil pump since my gauge was fluxuating oil levels. Seems like it's settled now. My advice, replace all the little additions to the engine like the PCV,oil sensor, etc.. since your putting in a new engine anyway. The cost isn't that much, and will help eliminate those little problems.. Your right, the warranty is pretty good.....
2015 Jeep Rubicon Hard Rock, 2000 Jeep Grand Cherokee