I can't tell if this Dewalt drill has multiple speeds.
This drill definitely has speed control (I've got the data from the DeWalt site in Russian, pretty sure that USA site has that data too) - it is claimed to have 0-2500 RPM controlled by how deep you press the switch button. However it will have rather low torque - around 11 Hewton-meters maximum and that's likely on the highest speeds (that's how drill motors work). The other problem is that you don't have fine control over rotation speed - all you have is a button with about 10 millimeters range and that range is mapped onto 0-2500 RPM so you will likely have hard time controlling the speed and you have virtually no direct control on the torque.
For your application you'll be much better off with a drill that also has a "maximum RPM" wheel on the switch - the wheel sets the maximum speed and how deep you press the button controls the speed in the 0-SELECTEDMAX range. This has virtually no control over the torque either.
The bottom line is this drill can be used for driving screws, but it's definitely not the best selection because of poor control over RPM and torque.