You may know of a systems installer but it is best to make sure that the company has installed your chosen brand of equipment previously. Each systems manufacturer has their unique way of doing certain things and having an installer who is familiar with the equipment/system you have purchased can save lots of time and headaches down the road. Ask for recent references and make the phone calls to ensure the installer can do what they promise.
Some processors opt to have their own employees do the installation. There is great doubt that provides any real savings and it may cost far more than paying experienced installers who will ensure that you suffer minimal downtime.
Typically, the installer is well qualified to handle all 12 and 14 volt electrical connections. Local licensed electricians or employees should be used for all electrical installation and connecting of 115 volts and up because they are more familiar with local regulations.