Garbage disposals that become jammed can be fixed rather easily. Usually a "key" is left that can turn the unit manually. Many times the unit can be loosened to work again (there is a small circuit breaker on the bottom that usually needs to be reset at the same time)
Here, the drains were leaking. Existing plumbing is evaluated for efficiency and durability. Necessary upgrades and improvements are made to bring the plumbing up to the point where it will be troublefree.
Here you can see the old brass "P" traps have been replaced with plastic traps. Brass will eventually corrode to the point where it must be replaced. In my opinion, plastic is superior in that it doesn't seem to deteriorate with age. Garbage disposal + installation usually around $120