Subaru Repair: conflict regarding transmission repair, bureau of automotive repair, transmission repair

Question
I had a local shop replace my overheating radiator. They forgot to put the transmission plug back, the fluid drained out, my transmission was destroyed. The owner, after much resistance, proposed I pay 1/2 of a found $1650 transmission. Besides the obvious of not accepting full responsibility for the error, is he now overcharging me for a transmission?
Thanks! This is nuts.
Pat

Answer
Without a model,year and other information about the vehicle,   I am unable to tell if you are being overcharged. Also there should be an alternate means to settle the dispute. California has the Bureau of Automotive Repair which deals with consumer complaints and does mediation. That would be advisable to look into.