Blender 2.49 FX exporter can export the whole scene or only selected objects.
One way can be to select all your object (key A in object mode) then menu : Object -> Join
this way all your text will be one object only to export to FBX.
If your question is how to transform Text to 3D, perhaps it is some Plugins for Blender or other methods ? (try google, ask on forums) ?