2000 SAAB 9-5 P0722 Code

Transmission problem
2000 Saab 9-5 4 cyl Automatic 175000 miles

I'm tired of dumping money into this car. Please help. My daughter was driving the car. She stopped at a signal then the car didn't want to go again. It justed revved like it was in neutral. She shut off the car then started it again. The car drove but the check engine light was on along with another light that looks like a sun with an ! In the middle. My neighbor hooked it up and got the P0722 code- he said it was a cheap part and that I could pick it up. I've been searching online and came up with a speedometer sensor that I found on eEuroparts. I have a friend that is a weekend garage mechanic who said he would help. I just want to make sure I'm buying the right part and also wondering where I can get a diagram that shows where and how this part goes in. Thank you for any help you can give me :)