I have both the program Reason and the keyboard http://music.yamaha.com/products/main.html?productId=36. Reason requires (I think) an MIDI keyboard, so my question is: would I be able to plug than into my computer and use it as a MIDI keyboard?
if you have something to convert the midi from the keyboard to the computer usb. i believe you can get the M-audio uno or you can get an audio interface that has midi I/O and connect it that way
Yes. According to the specs there is MIDI out. So run a cable from your MIDI out to your soundcard's MIDI in.
Just remember your options get cut down with budget Keyboards.