I just picked up a 2016 cclb dually it has cloth power heated seats I want to pick up some used leather heated and cooled seats. My question is beyond the dash switches is the wiring already there for this it does a different harness gave to be installed. Second concern do I have to program the ecu or will it just work with replacing the switches and seats
If you have heated power seats & wheel, with driver side adjust and the 120v outlet already, up should have the needed wiring to install a set of 2013-18/classic 4th gen seats. (Not 09-12 seats or 19-21 New body style 5th gen seats.)
Laramie, longhorn & limited seats will be leather, vented and have memory features.
You likely don't have the wiring for memory, but it can be added later.
The heated functions will work, the vented/memory features will require BCM changes yourself via AlfaOBD/OBDLink MX BT adapter... Even if you get the correct switch panel below the radio