If I understand your question, you intend to place ceramic tile over an uneven floor consisting of tongue and groove boards. This will require the addition of cement board such as this:
http://www.hammerzone.com/archives/flooring/ti le/prep1/cement_backer.htm other wise the floor will be unstable and the tile or grouting will eventually crack. It's not difficult to install, especially the quarter inch thick one, but it does require special saw blades and drills for cutting holes and adjusting the length or width.
Additionally, it requires screwing to the subfloor every 8 inches with special screws as well as gluing it to the subfloor with the same mastic to be used for attaching the tiles... Not as daunting as it sounds but does take time. I just finished about 160 square feet...