1979 Mercedes 300SD W116 Electrical Problems

Not the best mechanic here, definitely not the best electrician. Only my high beams work, low beams don't, hazards, blinkers, instrument panel lights don't work, tachometer wobbles back and forth with inaccurate reading. No idea how it works, if anyone could give me some pointers or a wiring diagram or anything that might be helpful, that would be greatly appreciated. Fuses look ok. Also the glow plug light stays on all the time, not when key is off though.