I have the mechanical things sorted, but now need to figure out how to get the 6l90 wired in and talking to the e67 and bcm.

I've heard many different "should" answers to this, but am looking for a definite answer.

Do I need the t42 involved?
Will I lose my gauges if I don't use the t42?
VIN programming required?

2009 GMC Canyon 4x4 5.3, 6L90 with new t43 programmed as a 2009 Silverado, NP241c with vss.