Yes, the OE shocks are gas and yes they can lose pressure over the years.
The toe can be checked in the driveway, but there are several things that must be done to get an accurate measurement.
Raise each wheel and use a jackstand with a nail clamped to it as a fixed position pointer to scribe a line all the way around the circumference of the tire. This does away with the inaccuracy of the tire mounting variations around the tire.
After scribing both tires, let it down and roll the car at least two rotations of the wheel to settle the suspension. Measure carefully the difference between the two scribed lines front and rear at the same height off the ground. Adjust so that these measurements are exactly equal.