Small plugs in head

My 96 2.5 came back from the shop with a diagnosis of blown head gasket. The oil did not seem like it was full of coolant, but I pulled the head this morning, and the gasket looked fine and there didn't seem to be any obvious cracks in the head. What I did find was these 4 small plugs in the manifold side:


This one here seems to have developed a hole in it. My guess is that this is the problem. My questions are:
What are these things called?
How do I get them out?
Where do I get new ones?

Or, is the the proper fix to JB weld a dime to it?

Thanks

What was the reason for the diagnosis? Lost compression? Water in oil? Oil in water?

Those are freeze plugs. Hammer with a punch on one side and knock it in, then grab with pliers and remove. Clean up the hole, use some Permatex (the hardening one - can't remember if that is #1 or #2 Permatex) and tap the new one in. Replacements are brass or cheap steel - try to get the brass. Napa will have them.

To tell the truth, I didn't ask the shop why they claimed that. I had it brought in because the freeze plug in the back sprung a leak. The shop changed that out. After that, they called me and told me that it was a blown head gasket and wanted $1500 to fix it. I let it sit for a while because I was going to junk it (passenger side is torn up from a collision a while back), but I don't like the Toyota I got to replace it, so I figured I'd have a go at doing it myself. When I go it all torn down, I noticed this freeze plug, which had been under the manifolds, had this hole in it. Now I just need to see if I can get to the back of it somehow. Any way to remove them without access to the back?

I'm taking the head over to the machine shop to get checked out Thursday. I guess I'll swing by Napa too.