Check bulbs, fuses, and check for wiring problems
It is probably the running lights that are working and the regular headlights aren't working because of the switch or wiring. TAke it to a garage.
Check the headlight switch, if not it's probably a fusible link in the headlight circuit.
This happened with my 2002 Blazer. The windshield wiper switch also had an effect on the radio. The dealership found two weak electrical grounds and that solved the problem.
Is it blowing cold air only or not blowing any air at all.
You need to periodically replace the headlights on your Chevy truck when the headlights start getting dim. You can purchase replacement headlights from retailers such as Parts Source.
Yes
yes, 82-93 are the same besides grill design
the 1996 and 1997 are the same and would not work in your 2000 straight from GM
Probably a blown fuse. What you need to find out is why the fuse blew.
That would be the 4L60E
Need to know if the blower is working or not and if the air coming out is hot, warm or cold.
The blower resistor gets overheated and burns out usually because the blower motor is failing also.