Okay I'm technically not a first year coach.  I did a few seasons probably about a decade ago, but I digress.  If I wanted to run a halfcourt press/man to man defense would I need to practice both press and man to man on defense? 

yes you would have to practice press and man defenses.

generally running two defenses is not the best idea since you have to put so much practice time into each and it hurts player development a lot.

If you really wanted to you would probably have to really focus on WE at least probably 50+ to make sure everyone is getting developed.

You just answered my question for me.  I was looking for the press without having to go fullcourt all the time.  But it hinged on whether or not I would need to practice both.  I just took over a DIII team that hasn't had a human coach in a decade so I figured get my offense and defense figured out now so my incoming freshmen can start building up their ratings in it so when the day comes that I might not suck so badly they'll at least know the plays!