Hello to you,

Since your ultimate purpose is to write scores and publish these scores or edit the scores then replay or publish them, My question would be how much are you willing to spend.

There are very specialized midi sequencer/score editing and publishing software and there are various softwares that support scores but not very specialized in it. Furthermore, it also depends on what you really want to do: do you actually want to record audio and burn cds for your audio?

In terms of hardware, you will need a midi adapter. That is all.

I know I am not giving you enough information to start the project, but I am giving you enough information to ask more questions and provide more information about what you need; so we can assist you for the second step.