Big Tuna

I am planning on replacing the 5.4 on my 2004. The #8 plug broke off and will not come out with the lisle tool.I even took it to a shop and they said they had never seen one stuck that bad before. They recommended me to another local shop to have the head pulled to get that plug out but I was quoted $4,500. I don't think it's worth it to put that much money into a motor with 100,000 miles on it. My question is would it be better to but a rebuild long block with the warranty or should I rebuild the motor my self with forged internals, comp cams rebuilt heads and have the block bored 30 over. If I bought a rebuilt long block where is a good place to but it from?

As a side note I contacted the stealership where we just bought my wife a new ford edge to see if they could help me out with the cost of a new motor and they said to replace the motor would be a minimum of $14,000. All I could laugh.

Thanks for the help