'04 Tahoe pwr seat addition

[cj2546]

I have a 2004 Tahoe LS with 6-way power driver seat & manual passenger seat. I want to upgrade to 10-way power seats to both driver & passenger side. I know the BCM has to be reprogrammed and I've heard conflicting reports about needing a "crossbody" harness (GM 15196653). Can anyone tell me whats involved in performing this upgrade?