Shop says I need a new throttle body

My 1999 3.8L 6cyn Firebird had been running great and then it just quit running when I was driving. It would turn over but not start. I had to have it towed.
It wasn't throwing any codes at first and the mechanic thought it might be the ignition module but he did a pin test I think and has ruled that out.
Now he's got some codes and says I need another throttle body. He's looking for a used one because a new GM throttle body will cost over $700.00 Ouch!!

So, Does this sound right? Don't mechanics usually replace parts that are connected to the throttle body? He says he's sure this will fix my problem.

Thanks

Update: Bad MAF sensor. Well, after leaving my car with the new mechanic for 3 days and nothing being done I decided to have my car towed to another shop I've used before which is where I should have taken it to begin with.
They replaced the Mass Air Flow Sensor and everything works great again. It cost me $247.00 because the screw heads broke off because of rust and the they had to drill the holes and put new screws in.
So, if your car stops running suddenly it may not be fuel or spark related but your MAF sensor.