Documentation is good at a technical level but it is lacking at a user example level, no doubt about it. I hear that a lot of effort is going into documenting v1.0, but that is another story.
I found that the best way to figure things out was to install the demo site on a local server and just let it rip. I keep a few sandbox installs on my local server and work things out, test snippets, and general hacking (if needed). The demos site has some good examples of how things are done. The 2nd most helpful thing was the MODx for beginners tutorial in the wiki (as well as other wiki articles). And definitely this forum, I think that the lack of hands-on documentation makes it so that the community is much more helpful than most other user communities I know. Believe me there are some things that you just need to ask, but this is no excuse for not searching first
To link to a page within the site use [~xx~] where xx is the id of the page you want to link to (the id is in () next to the doc name in the doc tree).
BTW, welcome to the club.