No way, it's not so symply thing..
I suggest you to start read some good book about it in order to divide your digital modulation in sub-block. There are also some basis thesis on the net that you can find about this arguments.
Moreover it's better to focus directly on the kind of modulation you've to realize..
Done that you'll have to design each single block and make the datapath pass throught them.
It's also a lot important that you know the datarate in all the parts of the project expecially if in some point you've to mux different kind of signals (example the varius sync that usually are generated internally).
Done that you'll have also to design digital filter in order to shape the spectrum as you need for your modulation and that's another problem..