Hi Nathan,
Just to add to Jim's reply, Dee Why is a really nice area, It has excellent public transport links as mentioned on the main road (Pittwater Road) the city is about 35 mins away by bus. Away from the main road the housing areas are quiet and although I've not lived there, I'd certainly recommend it as a place to start. It has a wonderful beach with a pool and great local amenities - public library, shops etc, It's also close to Warringah Mall for larger stores and supermarkets. I guess it must be about 4 or 5km from Manly, so can't be far to the hospital.
My partner grew up in the Northern Shores area and it's one of our favourite places to go to get out of the city - Avalon, Newport, Narrabean and Collaroy are not far up the coast road with loads of great cafes, bars and restaurants (and beaches

) - It's also close to two major national park areas, Garigal and Ku-RIng-Gai Chase if you want to get away from it all
Enjoy !
Neil