Pressure sensitivity can not be a plain 1/0, on/off kind of signal.
Well it can but I see what you mean now, thanks.
If you take what is in effect an after touch reading and apply it to the note velocity in the MIDI note you will get a passable velocity sensitive keyboard. I have done this with a keyboard made out of coins and a capacitave touch sensor. The touch sensor reading is different depending on the area of the contact you are covering with your finger. So a heavy touch spreads out the pads of your finger and gives a different reading to a light touch which you can map into the note's velocity. It is better than nothing.
Given the OP said :-
I'm brand new to this site, and to Arduino.
Then I think this is an overambitious project. Although doable he has a very steep learning curve ahead.