Developmentally, basically count from when they should have been born (handy to know the estimated date of delivery and use that). Growth is also charted according to when they should have delivered, until their second birthday.
Feeding - as above, if needs tube feeding then you would have to be trained in doing this. I'd say that the majority of ex 30 weekers go home taking sucking feeds. Depending upon weight gain etc may well be on a prescription formula, which would need regularly prescribing by the GP.
Breathing: hopefully a 30 weeker won't be needing home oxygen. If they do, there will be quite a bit of organisation/training required, but you would get extra back up.
Immunisations are done according to when they were born, not when they should have been, so often have started these whilst in hospital.
Medications vary, according to what problems they've had. Many will be on some combination of vitamins/iron, though that can vary according to factors like whether or not they still need prescription milk.
Temperature control tends to be more of an issue than in term babies. They won't be let leave the hospital until they can maintain their temp well wrapped in a normal (solid sided) hospital cot. Bear in mind that SCBUs tend to be kept warm.
Illnesses: ex premmies are a lot more vulnerable to the winter illnesses. This time of year, the big danger is bronchiolitis: starts as a nasty cold, then feeding starts to go off, breathing gets faster and harder, and they can get very ill. Basically, if their feeding goes off, they need to see a doctor that day. They tend not to get a fever if unwell, though a few do, but instead are more likely to drop their temp. So a low temp is just as worrying as a high one.