No need to join AANAC unless you have money to burn. Don't waste money on 1-day seminars either. It can't be learned in a day. Nor would you actually retained the knowledge without doing the task on a regular basis.
If you have the MDS RAI manual (Revised December 2002, updated August 2003) and an actual on the job training, everything will fall into place. MDS info is easily accessible on the web. You can even post a question in the Geriatric forum here.
I can also hook you up on an MDS help site with instant answers from seasoned MDS experts (non AANAC affiliated).
MDS 3.0 implemented in Jan 2004 is not feasible. They just put an update in August 2003 for the MDS 2.0, now they're gonna dump it? Software companies still have to do a beta test on it, too. Jan. 2005 is the intended target date but it can always change since it's still under scrutiny. Either way, CMS would provide all of us with ample time of the actual dates... including extensions ...
My advice regarding the MDS career -- PURSUE IT! The demand is great and the opportunity to work as a consultant is brighter, not to mention ... $$$$$$