Alright I have a 2007 tc and have been wanting to install an aftermarket deck. But I know In some cars the radio is part of the brain. Is that the case with my tc.

 

So I need to know if I need one of the expensive harnesses to put an aftermarket deck in my 07 tc.

 

For the tC, all you need is a standard Toyota harness for the wiring portion. There's nothing really special about it. You will lose your steering controls for the radio unless you get a separate steering wheel interface unit like the Metra Axxess ASWC-1. Not a big deal if you don't care to have the steering controls.

 

i know of no car where the radio would contain any parts of the car's ECU..

no expensive wiring harness. it usually runs between $5-10 for the wiring harness.
then as bbsciontc mentioned, you'll need another adapter to keep your steering wheel controls.