Providing these drain leak things are fine there is the chance that the cord running to the disposal has developed a short or a wire has become disconnected. You will need to disassemble the unit to verify all wires remain securely fastened. The last conclusion is that the motor has burned out, in which case you will need to replace the disposal unit.
To find a plumber, all one has to do is flip and run through the Yellow Pages or do a search on the Internet. From there you will see loads of plumber whom are advertising to get your job. The next thing you should do as a consumer is to take remember that there some plumbers whom advertise 2 different ads in the same place. Thus it is important to not water line repair make a rush decision. Look through the list of plumbers available and call a few (minimum of 3).
One other common design that is considered "washerless" was made famous by Delta and copied by several other makers. It uses little "cup" seals that fit over springs recessed in the back of the valve body. The springs press these "seals" against the cartridge and regulate the flow through little tapered openings in the cartridge. If you have one of these and it's dripping, changing these springs and seals will usually correct it. Here's a tip. Once you have the cartridge out of the way, insert a phillips screwdriver into the seal and pop both the seal and spring out. Stick the new ones on the end of the screwdriver to help guide them into place. This is especially helpful if you don't have long slender fingers.
Depending on your repair job you might need a bucket that will fit below the sink trap, as well as some rags and newspaper. Masking tape is useful for labeling and for wrapping around the heads of the wrench to protect your chrome tap handles. Rubber gloves are recommended, particularly when working with the toilet, but there are greases and glues that you may not want on your hands.
As with anything, when you are not sure how to fix a plumbing issue and when you don't have the proper equipment, you should contact a professional. They can usually find out what the problem is and resolve it for you in a short period of time. They will also be able to tell you if you have any other problems and water line repair they can suggest resolutions.
When doing the install on a water heater, keep an eye out for unconnected pipes. A commonly missed pipe is the one that leads out from the area for drainage. It is probably a recirculation pipe; that helps your water remain heated without wasting too much water.
Find out if the plumber works on a 24 hour basis and, if so, what are the extra charges involved. More important than the costs however are the person's trustworthiness and reputation. After all, he or she will be in your home and around your possessions. You should feel comfortable with their presence and confident that they are honest.