I found a vertical crack, about 1 inch long, along the upper part of the disposal housing. The unit, an insinkerator badger 9, is from 2010. When water goes through the unit, a small amount will drip. The amount of water is actually quite limited, even when using lots of water to wash dishes. The unit is obviously old, but seems to work fine otherwise. What are your recommendations? Replace? or just catch the dripping water (1 table spoon per day).
The good news is that a leaking gasket can be easily replaced. Most home improvement or local hardware stores will carry them, and they are usually inexpensive. However, depending on the particular model of your garbage disposal, it may require a specially fitted rubber gasket. To ensure that you get the right gasket the first time, write down your garbage disposal’s model number, take it to the store, and ask an employee to match it up for you.
A sink flange is the uppermost portion of a garbage disposal.  It is the point where the sink, drain, and garbage disposal meet, and it keeps debris from clogging your drain.  If you have a leak at the uppermost area of your garbage disposal, the source is likely your garbage disposal flange.  The two most likely reasons for a flange leak are that the mounting bolts have loosened and that the plumber’s putty has failed.
Another common cause for a leaking garbage disposal is the disposal flange. A leak at the very most upper area of the garbage disposal could be the garbage disposal flange which goes through the sink. A garbage disposal flange should be sealed with Plumber’s putty and then tightened from underneath the sink. If this is not tight enough or if it has managed to come loose (which can happen) then the garbage disposal will have to be taken down so the flange can be resealed and then the garbage disposal can be rehung.

Garbage Disposal