Dropping the valve body is an essential part of installing the Transgo kit and involves dropping the tranny pan, remove the tranny filters, and undoing like 6 bolts on the valve body. See an older writeup at
http://liberty.eurekaboy.com/transgo.htm (Note the resistor mentioned is no longer used as, IIRC, the TCM just "learns" around it).
I'll leave others who know more than I to comment about this product vs simply installing a transgo kit. The latter does not appear at all difficult once you have pulled the valve body and the cost is much less. Yes I do have a transgo kit but SunCoast did the install as part of my TC upgrade.