/diy/ - Do It Yourself

So I need to build a motor speed controller with these specs:

Operating voltage: 36V
Maximum Current Output: 15A (But will rarely need to supply more than around 12A)

Maximum input voltage: 40V
Minimum input voltage: 0V (or whatever, it will never reach below ~30V anyway)

PWM controlled (via 5V PWM signal from a microcontroller)

That's about all the specs that are absolutely necessary. I've been doing some hunting and so far the best guide i've found is this one:
http://www.instructables.com/id/DIY-MOSFET-Motor-Controller/

This guide, however, falls short of my voltage requirements. I'm an electronics engineering student, but unfortunately I don't have any direct understanding of these circuits so i'm struggling here.
How can I change the above guide so it meets my voltage and current requirements? Or if that's too big of an ask, what should I research in order to find out?
My assumption is that finding MOSFETs better suited to the voltage and current ranges I need would be the solution I seek.
How wrong am I?