Recovery from Current WAL (8.2)

From my reading, I can use PITR recovery to restore my database to its state
just prior to a recent change (not even an hour ago). The erroneous change
resulted from an UPDATE with no WHERE on a small table (<700 rows); I
mention this only in case there is a simpler recovery technique I can use
for such a small subset of the entire database.

The docs state that restore_command is required in recovery.conf, and that
the server will check pg_xlog/ for any requested files not found in the
specified archive location.

Can I use a command that points to an empty directory as the archive
location to force checks to pg_xlog? Or is there some 'cleaner' way?

Also, I read in another post (about v8.1) that the WAL records are written
in 16MB segments. If the WAL containing my recovery target hasn't been
written yet, how can I determine when it has and is available to me?

I'm running 8.2 on CentsOS 5, if it matters any.