I always do the rear main, when replacing a clutch. It's cheap, and easy to do, since you are right there anyway.
Always resurface the flywheel.
Always replace the pilot bearing.
Replace the throwout bearing, if needed.
Take a look at the tip of the input shaft on the tranny. If it is excessively worn (from a bad pilot bearing), I have replaced the bearing with a wider one to get to the "good" area of the input shaft. You need to do some measuring/test fitting to make sure a wider bearing will ride on the machined area of the input shaft.....the non machined area is larger diameter and will put a side load on the bearing and it will likely fail. Mine was within thousandths of an inch of having the proper clearance, so I am not sure if a wider one will work in all applications (depending on manufacturing tolerances). I did have to bottom the pilot bearing out against the end of the crankshaft (once the flywheel was installed), in order for it to completely ride on the machined area of the input shaft Of course, 2 other options are....replace the input shaft, or build up the tip of the shaft and machine it back down to the proper specs.