Once I've gotten enough of the terrain generation basics, I'd be happy to do a basics tutorial. But first I'll do something I know about, Skydomes.
Terragen seriously does have a lack of detailed documentation. And no. Scanning forums is not a good alternative. But then, it's an immensely complex program, and because of the render times, also very time consuming to do a tutorial for. Something that's already very time consuming. Having a wiki that has more than 20 tutorials would be very nice. Especially considering how a number of the current tutorial links are now dead. A fact I noted a while back in an older scene.
At least Terragen isn't as bad as UDK though.

. Seriously, until this year, there was almost no useful information on it. Though there was an overabundance of useless information.