The trans-go kit is part of the Suncoast kit that I have in my transmission. You do have to take the trans out and disasemble part of it to put the trans-go kit in the pre 06 trucks as you have to drill and put restrictor valves in the C-2 clutch drum. While you are in there this far you might as well replace damaged clutches and upgrade your TC as well. There is a few more things coming soon that everyone should consider as they help clutches live longer, but I am sworn to secrecy!
Don't worry, the worst part is actually getting the trans out of the truck. Opening up the Allison is pretty simple, just take your time. Also, if you are considering the kit from Suncoast, They also offer a service manual for the Allison transmissions. I have one and it is a great resource. Suncoast stuff rocks!