i was driving my 86 2.1L westy up to tahoe sunday night when i noticed
oil on my rear window.  pulled over and saw that at least a quart of
oil had been blown out of the dipstick tube.  engine was clearly
running on 3 cylinders.  i added oil and limped back home.  last night
i did a compression test.  150 psi in the cylinders that were firing,
0 psi in the one that was not.

could this be anything other than a piston ring failure?  is it normal
for them to fail so catastrophically?  engine has about 180k on the
clock and everything looked normal in an oil analysis done about 2k
miles ago.  valve springs seem ok from visual inspection (is that
enough?).  is there anything else worth checking?

how likely is it that i scored the cylinder wall or did other damage
to the engine during my 30 mile drive home?  will i further reduce the
"rebuildability" of this engine if i continue occasionally driving
(have to move the van twice a week to avoid parking tickets)?  should
i pull the spark plug and/or fuel injector power for that cylinder?

the body on my van is pretty rusty and shot, so i'm not sure it's
worth the effort and expense to install a new engine... how feasable
is it to rebuild one in place?  could i just throw in new bearings,
piston rings and head gasket? or maybe just replace the one that blew?
 or is it likely that the cylinder is all tore up and needs to be
bored?

i'm planning to leave the country in the next year, so i really only
need to get another dozen or so road trips out of my van before she
retires... she's not used daily.