Speedo Problem

Hi, kinda new here. I own a 97 corolla. My speedo stopped working along with the odometer. I got a check engine light and found out it's my speed sensor. I tried the local autozone and such and they don't carry it. Where can I get one and how much does it generally cost? Any information on this would be greatly appreciated. Also do I have to take apart the transmition to install it or it relatively simple?