[RMVX ACE] REPUTATION: HOW DO I CODE THAT?

In a previous forum post, I asked a question about how to make quests more interesting, and a few people mentioned adding a reputation mechanic where in doing quests increases affinity with that NPC.

I like that idea, but the question is: how would you do that in a game?

This is a question of coding. I use the RPG Maker VX Ace engine, if that matters. Let's use the example of my first game "The Bamford Tenement" about a guy who moves into a strange tenement and does quests with other tenants. It was fairly simple in it's design, but let's see how we can make it more interesting with reputation.

Say Clouse (Protagonists) does quests for Dante (NPC). How would I write a script so that each time Clouse does a quest for Dante, it raises or lowers reputation with him based on the player's actions? As an edition, how would you create a mechanic where you could go to the pause menu, click on a tab for reputation, and see your standing with each character?

I'd like to do this without using plugins, because I fear that if I publish a game with plugins, I'd had to give royalties to the person who wrote the plugin. By the same margin, it may not hurt to show me a few plugins just so that I can read the code myself and maybe learn a thing or two when coding in the future.

Other than that, what do you guys think of reputation systems in general? Any games do them right? Any games don't do them so well? What are your thoughts?

All feedback is read and appreciated. Thank you.