Yep. You have to drive it to the surface, or let it float up of it's own accord- hence the need for positive buoyancy. If you have a sealed tank, the pump compresses the air as the tank fills with water, but geared pumps leak a bit, so once you stop pumping, you'll find the pressure in the tank gradually pushes the water out through the pump, ruining your trim. That's why you need the valve.
There is a third way, but that involves making a snorkel, which may be a little tricky for you. Keep it simple.