Custom module/block to create forum topic from user input

Hi, I would like a block on my front page that does this:

Has a single line text box for post title
Has a multiline text box for post body
No other user options
"Submit" will save data, and prompt user to register/sign in then return to that block (or a dedicated page for same info)
Submission (once user is authenticated) will be created as a new forum topic (the same forum every single time)
The user will automatically be subscribed to the thread
The user will then be taken to the forum thread itself

ie. a visitor arrives, gets to ask a question with a minimum of fuss (login or quick registration without have to find their way around the site), and their question is converted to a forum topic, they are subscribed, and shown the thread.

I am not sure what is the correct way to acheive something like this, but I was thinking some sort of module+block would be best.

It would be helpful to tell me what sort of ballpark cost to expect - I have never paid for development before.

tony@tall.co.nz