The headlights work but turn signals don't and hazards don't work either and brakelights still don't come on.

Most likely its your turn signal switch. For some reason GM decided to run all the lights except headlights through it. You most likely don't have brakelights either. Sometimes you can verify by pushing a little forward or backwards pressure on the hazard switch and everything will start working.

YOU MIGHT HAVE A BURNT OUT RELAY IN FUSE COMPART UNDER YOU CARS HOOD CHECK THAT OUT THRU YOUR CARS MANUAL,IT WILL SHOW YOU WHICH RELAY IT IS?

My first guess would be a ground problem.
The headlights and tail lights are controlled by the same headlight switch, but the brake lights are on a totally different circuit.
You may have to get a shop manual to get the wiring diagrams needed to troubleshoot the circuits if the ground connections are ok.
The lights involve the body computer and other components.

Could be the headlight switch.
The switch has two sets of contacts for the parking lights, the park position and headlight position.
You may need to check the circuit at the switch to see if you are loosing power when the switch is moved from park to head.

Hazard and turn signals usually use separate flashers, switch the flashers to see if turn signals work and hazards don't, if so replace the flasher

you need to replace the blinker flasher unit

it is different from the hazard unit

they cost about 4 bucks

the flasher unit is the big round thing in the fuse panel in the dashboard

My first thought would be a bad ground connection in the harness for the rear lights.
You might want to take a test light and check the contacts in one of the sockets.

The turn signal and brake lights are controlled by the turn signal switch.
You did not mention parking lights so I will assume they work.

Could be a faulty turn signal switch or a wiring problem between the dash and the rear of the van.
Do the hazard flashers work on all four corners ?

suppose you headlights are broken?

try turning hazards on off n see that makes a difference if so u need new hazard because ur turnsignals are routed through that switch... if not most likely the turn signal stock is bad if playin with hazard switch doesnt change anything

1. Check the fuse make sure it is not busted and also use a designated amp only.
2. Check the bulb and the wires also.