What are good part (like air filters/oil filters/battery etc) (decent and cheap) stores? What are different car fluids (like transmission, coolant, brakes, power steering and not sure if there are more) and when and how often one should replace them? What kind of services brake need? I heard few things like brakes pads, rotors, caliper and brake fluids. How often one should check and when to replace them? If replace them then what should be replaced? all or some parts?

1995 Nissan SE V6 pick up with extended cab & 4 wheel drive Tailights and instrument (dashboard) lights are all out. The headlights come on OK. Double checked fuses with test light and VOM. Pulled the rear lenses and all bulbs are good and work with test set-up. Checked connection block at both rear light assemblies and find no voltage. Traced both harnesses to connection block under the bed just forward of the tail gate and no juice there either. I trace this main harness that runs up under the passenger side of the frame & into body channel just under door sill. I put the car away for today but I'm planning to look around under the dash. I'm also thinking that the headlight switch could be bad but I figure I'd ask if some has had experience with this problem before and could point me in the right direction. Thanks for your help.