I need help creating a mod, I have very little experience!

This might be asking too much, but I’m trying to figure out how to create a mod that makes the illnesses in The Sims 4 potientially deadly. I’d like to make it so that all illnesses are similar to the “Ancient Illnesses” Sims can get, but perhaps without anecdotes? And a bit more lethal that the ancient illnesses. I’ve done some searching and can’t seem to find a mod like this one, so I thought I’d attempt to make it myself, but I have no idea where to start. I have Sims 4 Studio on my laptop, but haven’t used it before. If anyone could give me a little bit of information on where to start, I might be able to figure it out myself. I’m willing to do this myself, but I would be grateful if there was anyone who was willing to do it for me instead. Any help would be appreciated!