What they said. Definitely worth it to learn how. It's actually how I (attempt to) rationalize to my wife the expense of fishing. Hahaha...
First few will be slow, but you'll get the hang of it pretty fast. And by "mud line," I believe he was talking about the line of blood that runs down a fish's spine.
Easiest to fix, in my opinion, is a trout. Pull the guts out and cook. I even eat the skin. My wife doesn't, but the skin falls off, so pretty easy to avoid.