My 5 month old has cross eye and her dr wants her to be checked by an eye dr. And waiting for appt. I'm freaking. What to expect! How is ittreated?

Don't freak. Identifying and treating the problem early will avoid serious vision issues later. Depending on what the problem is exactly, there are a variety of treatments, from surgery to just covering her stronger eye to force her to use and strengthen the weaker one.
Understandable. It could be something as simple as her being too farsighted. Or it could be something obstructing vision, like a congenital cataract. Whatever it is, it has the potential of reducing vision in the crossed eye so keep the appointment. Hopefully it is with a pediatric ophthalmologist. If not, see if you can find one and get an appointment there!