1998 Cadillac Seville no spedo check engine and hard shifti

Transmission problem
1998 Cadillac Seville V8 Four Wheel Drive Automatic 98k miles

Hello I have 1998 sls with the northstar

My problem is this my spedo stopped working from time to time then the check engine lite came on and the the transmission would not shift out of 1st in less I gassed it up to 4k rpm them it shifted normal but still no speedo and im getting lousy fuel milage, can you enlighten me on the problem before I spend my kids college money on repairs I dont need, is it a sensor or is it major. I disconnected the battrie and it still did the same.



i went to auto zone and they told me it was the speed sensor also, however they had 2 different ones. My question is this does the speed sensor go from the throttle body to the tranny? If so is it a hard fix