Harness info here if you want to modify a JY harness. Really not hard, but a huge time killer. Also $75 to unlock your ECU with whatever options you want to use. (note not a tune, you will still need the ECU updated for cam swap more powa etc.) \
Or go easy and FITech LS controller. Easy plug and play with new harness. Requires some handheld tuner configuration.
I suggest a full Elring/Reinz gasket kit w new MLS headgaskets. Easy freshen up and just check the cam and bearings for wear and replace as needed... Great time to add a cam
LSs are tough, just make sure the oil pump is good and you should be set!