I have a 96 Pontiac Grand Prix..., & The Left Turn signal isn't working... in the front or the back.., also sometimes it blinks slowly or doesn't blink at all on the right side, I already Replaced the Relay & the Fuse in the dash by the passenger door looks fine.., also in front there are about 4 bulbs that aren't lighting up in the center headlights, IDK if that's the brights or what..., it seems strange to me that that many bulbs would all be burnt out at the same time..., So Is there a Fuse Box I'm missing somewhere..., & On a Separate note my Front Driver side power window wont roll down..., thinking maybe that's a switch because the others work ok..

More than likely it's not all the bulbs that are burnt out. Your head lights work like a relay if one bulb is bad then none of them work. Try looking for the bad bulb (this will require you to pull the head light assembly a part to look at the bulbs) what you are looking for is blackening around the clear part of the bulb, also if you pull the bulb out of the socket and give it a bit of a shake does it make a rattling sound? If so then it's bad.
In regards to your left turn signal have you replaced the bulbs or check to see if they are burnt out as well? The also operate as a relay and will not work if one is burnt out.
You may be right about it being a switch. If you have the time, take the door panel off which can sometimes be a pain, **** worth it. Check to make sure the wires are still connected properly. If they are then i would look in and around the window tract to see if there is anything that could be impeding the window from going down. Other wise it could be a bad button system and just the drivers side button is shot. You may have to replace that. Hope this helps. Good luck.