How much would it cost to replace a freeze plug?

What is your question?

well I want to buy this Dodge Avenger R/T 2008 3.5L v6. She says the freeze plug is rusted out and needs to be replaced. I'm trying to figure out if I can do it myself or do I need to take it to a mechanic and how much would it cost about. It doesn't drive to far she said that it would need to be towed or it will overheat.

What makes this problem better or worse?

freeze plug needs to be replaced it rusted out

How long has your 2008 Dodge Avenger had this problem?

6 months