OK, since I'm here, I will admit the true extent of my ignorance.  What do
   I need to upgrade to netbsd-current?  My machine is not connected to the
   internet, so I can't use SUP.  So, my guess was to go to 
   ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-current/tar_files/src/ , download
   sys.tar.gz, install the sources on my machine, and reconfigure/rebuild the
   new kernel. Am I oversimplifying?  What else would I need to to, or am I
   on the wrong track entirely?

it's normally a bad idea to run a kernels and userlands from different
vintages.  sometimes it's OK, and for most programs it doesn't actually
most of the time, but a few of the system programs may not work.  in
netbsd 1.2 -> current, it's made worse since the reboot(8) program from
1.2 won't work with current, and vice versa, an the mode of failure is
fairly annoying (kills off every thing else, then tries to reboot the
system, fails, dies, and you're left with _nothing_ happening, and no
way [*] to get anything back).

pk uploaded a recent snapshot of netbsd-current to ftp.netbsd.org in
the pub/NetBSD/arch/sparc/snapshot directory, and it's probably much
easier to extract this snapshot.
   
   Executing halt on NetBSD 1.2 does _not_ take me to the boot prompt.  

what does it do ?

   A second reason is that the machine is standalone until I get it properly
   configured, and it sometimes hangs on me.  <stop>a seems less drastic than
   turning off the power. This is a minor thing, really.  It just annoys me.  

you should probably type "sync" at the prom after doing this, as it
will attempt to flush disk buffers, possibly removing or reducing the
amount of fs damage...