Reddit reviews Basic DCC Wiring for Your Model Railroad: A Beginner's Guide to Decoders, DCC Systems, and Layout Wiring

Borrow a copy of Basic DCC Wiring for Your Model Railroad and The DCC Guide, Second Edition from your local library. I found them to be pretty decent sources for getting your layout wired up correctly.

As you said, fitting decoders to your locomotives is another challenge, TCS has decent photo guides for installing their decoders in many locomotives; I assume other decoder manufacturers have similar resources.

For controllers, I'm told NCE is pretty beginner-friendly, but I have not used them.

I went with digitrax because that's what the local clubs use, even though they're all HO clubs, it's still handy to have a local resource to draw on.

Then there's the folks that are rolling their own controllers, the folks using JMRI and their computer, and others.