Hello, Elizabeth. Some people have autonomic nervous system involvement as part of GBS/CIDP. These are the peripheral nerves that control bodily functions. Part of this is gut system movement (GI motility) including emptying of the stomach. this can become quite slow in GBS/CIDP and cause nausea. The autonomic nervous system also controls how open the blood vessels are so that blood can pool in the legs on standing. This causes people to drop their blood pressure and feel faint on standing. Not commonly, but it happens, if the autonomic nervous system is not working correctly, the eyes will get dry. So, autonomic involvement can explain three of the four symptoms. Balance is more likely involvement of the sensory or motor nervous system, the first due to not feeling where in space your body parts are and the second from not being able as subtly to compensate for changes in position.
More importantly, there are specific things that sometimes help compensate for autonomic changes. If someone gets easily faint with standing, it helps to stand up in increments (sitting up in bed for a little bit, sitting on the side of the bed for a little bit with feet over the edge, then slowly rising, etc). If this does not work, drinking LOTS of fluids–meaning up to a couple gallons or taking extra salt (which helps the body hold on to fluids) can help. If there is blood pressure drop with fainting and this does not work, I have seen people take a form o steroid called florinef (that people whose adrenal glands do not work right take for replacement).
For the GI effects, eating lots of little meals can help instead of the typical big ones. A medicine called reglan can also help.
For dry eyes, lubricating drups (Tears Naturale or similar) can help. It is also worth having someone make sure that your eyes close completely with blinking or sleep.
I hope this helps.