Yes, those screws are the only thing holding that channel guide in. There might be some friction up at the window opening corner and there's a clip on the bottom of the guide to hold the channel in place. Reach in and give it a tug.
If it's original, there shouldn't be a key lock on the driver's side. The driver's side locks with the bar connecting it to the inside handle. Then you have to slide out the passenger door and lock that to secure the truck.
