Help! Editing Weapon Properties

Hi, I'm very new to Doom modding. My intention is to create a puzzle WAD that uses rocket jumping as the main mechanic. The problem is, the rocket launcher in Doom kills the player in two explosions. Can somebody help me change the properties so that it doesn't damage the player (it's fine if it doesn't damage enemies either), and, if possible, give it infinite ammo or make it not use ammo? Thanks for any help. I'm very new to this so if you can please walk through how to do this as detailed as possible.

Is the wad going to have enemies? If not you can just turn on god mode and infinite ammo. If there will be monsters, what port are you aiming for? It would be very simple to make this change in a port like zdoom or zandronum.

I will be using zdoom.