Save your money on the fluid change, as mentioned above it is not going to bring back missing gears. Since you have a scan tool you can scan live transmission data (if you have a nicer tool that does this) and make sure the pcm is commanding a 2-3 shift. The pcms are pretty forgiving in these cars in respect to throwing trouble codes for missing gears so you likely wont ever see one and have to troubleshoot by watching live data. Often times on higher mileage vehicles that lose 3rd gear is either due to 3rd clutches slipping and burning to the point they will no longer hold or the 3rd sprag is shot and will no longer hold in the lock direction, which either way means rebuild.
