Engine ran hot, now what?

I was going 60MPH for 20 minutes. Then it lost power. Gauges didn't show temperature until it stop, and I shut it off. It was very hot! I let it cool down. Filled it with water and drove it two miles to get home. It was hard to start. I think I had to give it gas to keep it running. I had a water pump issue that I neglected to fix. I just kept adding water never got hot. I check the oil for water. No sign of milky substance. Drained my radiator looking for oil. Which was hard because not much of water. Stared taking it apart. I noticed oil down in the intake. Not sure if it was from EGR valve over the years or if something like a crack like intake manifold? My questions are, is there something I can do to check to find the problem. Or am I jumping to conclusions on it being the heads? It's got 280,000 on it and I'm tired of driving it. But it's all I have and can afford. Advice would be appreciated! Thanks in advance! Guy with a non-running truck that needs to be working.