Pretty easy to do the full Ag Leader treatment. You will retain the factory seed sensor harness. Generally speaking you will need:

Display and power cable for tractor, mounts, GPS cable if desired.
Implement cable and tractor implement cable.
Seed Tube Monitor Module with Dickey John adapter cable.
Hydraulic Seed Rate Control module with White adapter cable(s). 
Pressure sensors as desired. 

Point row/section clutches can be automated as well if you want to. OEM row clutches can be controlled too.

Feel free to call text or email if you have more in-depth questions. Contact info in profile. I’ve done multiple White to Ag Leader swaps.

The planters are technically ISOBUS and should run on any ISO monitor, including the 1200. That being said I have one that we tried running ISOBUS and everything worked other than the seed tube monitor. It was one of those let’s try this and see if it works deals, and it didn’t so the customer just went back to running his AGCO display