If the 08 I-5 powered H3s have one, you need to send in both the PCM and the TCM (transmission control module). My 08 Alpha does. The trans module only has one broom style connector hooked to it. I learned the hard way as I only sent in a used PCM and then had to acquire a TCM to send them also. Since I was keeping the oe ones for warranty claims , I wasn't out of service waiting for them to get flashed and sent back to me. To get your speedo right the first time you should use a gps to record indicated and actual speed at 20mph , 40mph, and 60mph before removing processors. Be sure to be running the tyre size you will be using so they can set it correctly. My speedo reads perfectly as tested by a gps and the occasional speed indicating signs. Local PD uses me to accuratize their lazer guns. And double on what Alrock said about not bending the pins when reinstalling processors.
And be sure ignition is off and disconnect neg battery terminal before touching processors. Case relearn can be done with most modern scan tools such as the Snapon Verus , Solus or Modis. GMs Tec 2 not required. You can drive it with the sucks to be me light on till the case relearn is performed. Its all worth it in the end IMHO.