The best way to find out about ordering a meta42 is to PM someone who makes them, such as KurtW, JMT, erix, etc...
There's more than one way to PM someone. One convenient method is to click on the PM button located at the bottom of a message posted in a thread by someone you wish to PM. For example, if you wanted to PM me, just click on the PM button at the bottom of this message. That will take you to another page where you can send the PM. It's very much like posting to a thread in one of the public forums, but here you will find a recipient field, which must contain the name of the person you are PMing. After that, put in a subject (required for PM) and then enter the body of your message as usual.
Another way is to click on the 'user cp' button in the top right corner of nearly every Head-Fi web page. This takes you to your own user control panel, from which you can manage your Head-Fi acount. From here, click on the 'private messages' link (upper right). Then click on the 'new message' button (near-bottom center) and send your PM as described.
You can try it out by PMing me with any other questions/comments, and I can pretend like I know something.
As for getting a meta42, those who build them will help you sort out of the details, just ask them whatever's on your mind. You should have a clear idea of how you will use the amp, how much you can pay, etc. I think you can expect to wait 2-3 weeks from the time you finalize an order to get your amp, assuming the builder isn't too busy.
piece,
rp:AUM