Where are the freeze plugs located on 98 Jeep Grand Cherokee and how much money to fix?

I have 1998 Jeep Grand Cherokee. The freeze plugs are corroded and leaking. One mechanic told me it would be $80 to replace the one leaking one. Another mechanic told me that all of them are leaking and to replace all of them, he said it would cost approximately $650 to replace all of them parts and labor. Due to him having to drop the transmission to reach one of the freeze plugs. I am so confused as to what to do and who is right please help.