I'd say just get Overwatch for now and let it do its thing for a little while and see how you feel. You won't even notice it is there until you start seeing why it's there. Messages about stuck sims and cars deleted and suddenly you realize that's what's been slowing down your game forever and why didn't I do this sooner? :D
Story Progression is big but beautiful at the same time, it is just so helpful at keeping your town alive. But if you're not sure about it, take your time. There's no deadline, right?
Edit:
Oh and btw, I only ever figured out how to install mods by watching YouTube videos too. Once I could see it done I was able to do it. B)
