The black tube looks like a fairly standard light shield. It keeps the colored LED that is illuminating the needle from bleeding over into the face illumination. That is needed to allow the two to be different colors.
Can you get the part number off the GPS unit? That looks a lot like one that I experimented with for a vehicle tracker. When it worked it was great, but it was dooooooog slow getting satellite lock if it had been unpowered for more than about an hour.
Have you done any time to first lock tests on it yet? I am also curious if it has data smoothing in it.
