The work flow with fluid boxes is different from the work flow with Breakpoint views. Did you look at some tutorials about using Fluid boxes. Since fluid boxes have several limitations, you probably will have to change other things before being able to add fluid boxes. Forget the myth that conversion is done in minutes, that is not the case.
Fluid boxes cannot have groups, no stacked objects, no line shape, no highlight box, zoom object, rollovers... to mention some. That has to be cleaned, before you can try the option that will suggest Fluid boxes. Static fluid boxes have less limitations but they are not that 'fluid'.
As for text: normally it will rescale smoothly between devices. If you created the old project based on a good custom theme, changing the font size, which is now only necessary for desktop is just a breeze using the Object Style manager.