General questions before installing A833

I have a ‘71 Demon with a 360, and I’m getting ready to install the new tranny I bought. I also bought a new TO bearing. I’m 17 and have never installed one of these transmissions before, but the guy I bought it from said to lightly sand the collar that the TO bearing rides on, as well as the tip of the input shaft that sits inside the pilot bearing. What grit sandpaper should I use for this, and if not, what should I do to prepare the input shaft? Thanks.