If the problem is the Heater Control Valve (an extremely common problem) you may be able to handle it yourself. It's a VERY easy part to bypass and it's right up top and pretty easy to get to, you don't have to use any tools but a philips screwdriver make it easier so you can unmount it from the firewall. There's a thread in the FAQ section which covers the two most common causes of loss of heater function. The second problem is if the blower stops working... So it that's your issue, it's covered in the same place.
http://www.toyota-supra.info/forums/...resistors.html