Awesome story. Pretty much how I started tanking too.

My very first char, a druid and still my main and absolute favorite. Think I was lvl 21 or so at the time when I was asked to tank the Deadmines. Didn't know what tank meant either but I said sure. As soon as I got in there I went cat form and went in. Had never seen an elite before so I wasn't prepared for the beating that was soon to come. After the first wipe they asked me what the hell I was doing. I didn't answer so they told me I have to go bear. Sure, I thought and went back inside. They prompted me to go first and so I did, took a few hits and noticed that I'm hardly doing any damage. I shift back into cat and we wipe again. Now they ask why I went back into cat form, so I told them I don't do any damage in bear. This was a great group of guys so they all lolled and told me very politely that I'm the tank. I'm the one who takes damage and they're the ones doing it.
They explained the taunt button as well.

More than an hour and several wipes later, van Cleef was down and I've been tanking ever since.