I just took a wreck workshop, which was an introduction to the basic ideas of wreck penetration. There was a good lecture to open the class, touching upon the things that make penetration different, including silting, percolation, lack of ambient light, and disorientation due to the position of the wreck. We talked about ways to find wrecks, managing shot lines, and then went into line techniques and protocols. We practiced dry runs of line-laying and lights-out line following.
We then did two days of diving (NOT in overheads) to practice what we had learned. It was fascinating and very challenging. I actually wrote a pretty long report of the class on SB.
The biggest thing we learned was how far we had to go before we could even CONSIDER trusting our lives to line we laid and expected to follow in an emergency.
It was a very fun class, and I put the material to use a scant week later, diving the outside of a wrecked barge locally. My buddy and I found the skills we'd gained made that dive a much more enjoyable and relaxed experience for both of us.
I'd say that, if you can find a workshop like the one I took, it helps your general diving AND gives you skills to make diving the outsides of wrecks easier and safer. But there is a lot to learn about running line, and you can get into a lot of trouble very quickly when you're starting.
You might consider taking a DIR-F class as a first step -- If you're considering overheads, you're going to need technical gear anyway, and DIR-F is a great introduction to the diving skills (non-silting kicks, back and helicopter kicks, air-sharing without losing buoyancy control, etc.) that you need for overhead environments. Even if you didn't pursue further training with GUE, it's a great place to start.
