7 years old is not very long for a ducer to go bad, make sure you check the connection to the back of the unit and make sure the plug is not loose or something stupid like that.
If it is a bad unit, you can call vexilar and have them test it for you. They will have you take off the head, and just send the head, transducer, and power cord. They will test it and see what is up, if your transducer is bad and if the brushes need replaced.
I would suggest if you are going to restore it that you go ahead and do a brush replacement now. Brush kits are $30 from vexilar. If you feel you can do it yourself, you can get a brush kit from vexilar and replace them on your own. Here is the instructions for the brush kit, so you can see if it is something you can do on your own. http://vexilar.com/parts/pdf/vexilar_brush_replacement_kit.pdf
I think you can manage to plug in a new transducer, but yes it sounds like your transducer is going bad. A new transducer is about $90.