Why the multiple electrical problems '01 Mitsubishi montero sport?

My '01 Mitsubishi montero sport xls has developed multiple electrical problems, the radio turns on but no sound. Power side mirrors stopped functioning, dc elect. outlets don't work, headlight on warning stopped working. some lighting on instrument panel has also gone out. The car has about 120K miles on it and other than a minor fender bender, no other accidents on the car. Does anyone have any ideas what's going on and potentially what it might cost to get it fixed?