I have a damn good knowledge of cars, and I'm doing my rebuild myself, but when it comes to transmission stuff, I paid to have mine installed. I will do the valve body upgrade and torque convertor myself, but my rear end rebuild and gear swap I'll have done.
I probably could have done the transgo install myself, it doesn't look too hard and it does come with a video, but I was thinking better safe than sorry so I let a transmission shop install it.