Part that the spark plug goes into has expanded on my Ford Mustang?

So i recently purchased a used 2004 ford Mustang V6 (a week ago). The guy did mention that a spark plug popped out before and it now had a ticking noise. After some research, many people said it wasn't a big deal so i went ahead and got it.
Then yesterday the ticking got a lot louder and something sounded strange. My dad took a look at it and discovered that the spark plug has broken off into i think its called the cylinder.
So today he removed it, and that's when we noticed that the spark plug has some extra metal welded onto it or something. And that the cylinder (or w.e. Its called) was too big. So, that's probably why they did a shabby job and put extra metal to make it fit. Because when he tried to install the new one, it would've slid right through. And the porcelain was also broken off and i'm sure turned to dust or something and hopefully exited. But, some other little piece of metal, which i believe was the ground electrode, isn't there and my dad said it likely fell down in there.
So I'm going to get estimates tomorrow or Thursday. (My dad can only do so much)
But, i was wondering if anyone knew an estimate of how much it would cost to convert the cylinder back to its normal size, or what will have to be done and how much it would cost?

Its probably gonna be quite costly because the cylinder head will have to be removed in order to repair it correctly. They will probably weld the spark plug hole completely shut then drill it and tap it so you'll have new threads. The previous owner probably used some jb weld to temporarily fix it long enough so he could sell it to you. You might look around at the junkyards to see if you can find a used cylinder head.It might be cheaper than paying them to repair the damaged hole.MustangPartsSpecialties.com,
NewTakeOff.com, and DelkPerformance.com sell used take off parts off the Mustang so check with them too. The spark plug ground strap that broke off the spark plug is probably small and light enough to have been blown out of the exhaust manifold rather than damaging the piston or valves.Cross your fingers anyway. The previous owner probably stuffed some jb weld into the hole then let it dry and then screwed the plug back in the hole.