transmission feels like it is slipping
94 miata automatic trans, while driving the hold light comes on and rpm's go crazy feels like car is not in gear, I have to pull off road put in park and then return to drive. Had codes checked im getting 12 for poistion throttle sensor, 10 for intake air temp, 16 for egr position sensor, and 09 for water temp sensor. mechanic suggested it was the throttle position sensor to replace see if this fixes and clear codes, I don't trust anyone that wants to charge me 362.00 for part i can get for 70.00 and an hour labor for 15 minute job. Anyone have any suggestions before I start replaces sensors?