Hyundai Repair: 2001 tib oil chang conundrum, hose barb, head gasket

Question
I recently changed my oil and like another user, my car overheated there was a small amount of oil in the antifreeze so I am going to assume that my head or head gasket is blown also the hose barb to the overflow on the radiator  went away so that means I need a new radiator. I already replaced the thermostat. So... (#1.) Is there any thing else that you
think may need to be replaced? (#2.) Is this a common problem with the  Elentra / Tiburon. I have dune many oil changes and I have never had this prob before. The manual says 4.5q of 10w-30. I put in 4.5q 5w-30 (#3.) Is there that big of a difference between the too?  

Answer
If by "went away," you mean that the nipple melted, then you may well have a cylinder head warpage issue.  If the vehicle starts normally, the cylinder head is probably okay, but if it won't start or cranks for a long period of time, you probably need a new cylinder head.

Your issue has nothing to do with the oil change.  Nothing about an oil change on this vehicle has anything to do with overheating.  It's simply coincidence that the problem occurred after the oil change.  5w-30 oil is fine for your engine and will cause no damage.