You don't. Buy new or good used seat belts. Don't try to fix them if they are not working.
eBay.
$237
Go to any parts supplier.
In a repair manual.
Do a Google search for it or buy a repair manual.
In a repair manual or online.
I would start by purchasing a repair manual.
I'd suggest buying a repair manual.
Auto manufacturers are not required to repair automatic seatbelts that are malfunctioning. Auto manufacturers are only required to make sure there is not a defect in the automatic seat belt mechanism.
It would help if you could say what the symptoms are.
You don't. The faulty line must be replaced.
There are many vacuum hoses, consult a repair manual.