Doors and Windows - Replacing awning windows

I have a 50's brick ranch house with awning windows -- the kind that you crank and they swing out from the top. They have aluminum frames, are only single paned and have no weatherstripping. In addition, the cranks and mechanisms are broken on about half of them, and none shut very tightly. I would like to replace them with single hung windows, but do not know if it is a job I can tackle myself. I thought about buying a replacement for the smallest window (27 x28) and trying to install, but someone told me that a single/double hung window is incompatible with awning frames. Is this true? The windows look as though the frame would come out with the rest of the window.
Thanks for any help.