Although Sugar Gliders aren't normally susceptible to many illnesses, if anything should ever happen to one, almost any local Veterinarian who works on small animals will already be familiar with them.
Since they've been domesticated as pets here in the U.S. for about 15 years now, Sugar Gliders are nothing “new” to most Vets. However, the reason why most people in the general public have never actually seen one in person is simply because they breed SO slowly.
For example, as you can see in this photo , the mother has a “pouch” just like a Kangaroo. In this case, the mama actually has TWIN babies in her pouch - and on average she'll only have 2-3 babies a year. In other words, it's nothing like the responsibility of having “rodents” as household pets - which can often have dozens of babies in a single year.
Incidentally, this is also the reason why you will almost never see Sugar Gliders in “pet shops”. Because they breed so slowly (again, only 2-3 babies/year on average) it's not really lucrative to breed them commercially.