Have you checked the CEL???
It looks like it probably has a clogged oil cooler. That could be why it boiled over.
As for it turning off, I dunno. Possibly got too hot or maybe it has a ruptured EGR cooler and sucking coolant.
First thing would be to check that CEL and have it hooked to a computer that will read everything.
Like coolant and oil temps. If you are cruising the highway and the oil is 15-20*F hotter than the coolant, it is most likely a clogged oil cooler
Pull the EGR valve and check for moisture if you're concerned about possible blown HGs.
If it's dry, you're most likely safe. If it's wet, it's possible they're blown.
But DO NOT drive it until you check for moisture at least. If it has a ruptured EGR cooler and is sucking coolant, you will blow your HGs eventually.
azkcr is saying get yourself a scangauge or edge insight. These will allow you to see the actual temperatures, boost numbers, voltages etc. as well as reading the code(s) for your CEL (check engine light). This little monitor will save you a ton of money as well as your truck. Here's an example... or three!
I got mine before I bought the Ex. I used it on the test drive and new that I would be doing the oil cooler and EGR when I got the truck home (my oil and coolant temps were 20-25* apart). Just a few weeks ago my battery voltage wasn't coming up as quickly as it should after starting, I had a loose battery connection. I would never have looked at the batteries if the insight didn't tell me to. It's also telling me my FICM is on it's way out. My FICMV drops to 42-45 volts on a cold start. Comes right back up to 48 after a minute or two and I have no other issues (no smoke, hard starts, misses, nothing). Without the insight I would have no idea and if it's left long enough the low voltage on the FICM will start toasting injectors. I'll save myself the headache and a lot of money by changing it now.
As for what to do now... check under the EGR valve for wettness like the others have said.
It's the small black top beside the oil filter housing with the pink dot on it. Take the bolts out and pull it straight up, you don't want to pinch the valve hanging off the bottom.
Get the insight (or scangauge) and check your EOT and ECT on a flat section of highway at 65 with the truck at operating temp (ECT 190*). If the temps are >15* apart you need to do the oil cooler and since you're there the EGR.
There is a whole list of other upgraded parts to replace if your going in that far (I think I did most of them when I did my oil/EGR coolers, they're in my sig) but I'd figure out what NEEDS to be done first.
Good luck! I absolutely love my Excursion and after wrenching on it I love it even more!