Matt,
I've got the Lentech VB in my SC and love it. I ordered the level II which is about the same as a medium setting on the Trans-Go shift kit I had previously.
It shifts firm but not rough or hard in the automatic mode, but when manually shifted it hits the gears twice as hard. You feel it most on the 1-2 shift. I could not avoid chirping the tires on the 1-2 shift, unless I let off the gas while shifting.
Like George said, just unbolt the entire valve body you have now and replace it with the Lentech. I'm sure you could sell the valve body you have now with the shift kit already installed for about $125-$150. Drilling the hole and wiring a switch for the solenoid is easy.
David