The spark plug tube seals prevent oil from the valve train from getting into
the spark plug tubes.  The spark plugs are at the bottom of a fairly long
tube, and the ignition wires have a solid extension to reach the spark plugs
from the top of the valve cover.  Changing the spark plug tube seals
requires removing the valve covers, so the job is more involved than merely
changing spark plugs.  To see what is involved in replacing the spark plug
tube seals, go to this web site:
http://oregonstate.edu/~tongt/camry/index.html, choose Generation 2 Camry
(1987-1991), then go to the Engine Mechanical section and scroll down to the
bottom of page EM-101.

When you pull off the spark plug ignition wires, if they are dry and
oil-free, the spark plug tubes are OK and do not need replacement.  If the
bottom of the tube is filled with oil, then they need replacement.