Since it's our race-I'm in.  Sounds like fun.  I guarantee you'll get some advice-ultra people love to talk about ultra running.  
 
I would say if you've run 30 at McN-you could follow a real similar training program.  Maybe just add a bit of mileage to your long runs.  But really, there's not a ton of difference between running 30 and 50 (I know....20 miles).  But really, the training, in my opinion, is really similar.
 
Mike Klop

If you want some good night running advice come pace me for the last 40 miles at the Kettle Moraine 100 miler the first weekend of June.  Only a 3 hour drive up there, probably hit the 60 mile mark around 6 or 7 pm and run until finishing (would hope before sunrise this time).  
Night running is not really what would be needed for Farmdale I know for me getting ready for my first 50 miler was just doing a couple back to back marathons (Sat and Sun, not one weekend and then the next) or do a marathon on Saturday and go back out and run another long 15-20 on sore tired legs.  You just need time on sore tired legs, that is why I suggested pacing for 40 miles at Kettle, not to tough of a pace but will give excellent training for that and plus will be able to see what you think you will want in drop bags, eat at aid stations, etc.
A couple of books that I have if you want to borrow that I found quite helpful are:  "Running Through the Wall, personal encounters with the ultramarathon" by Neal Jamison and "Fixing your Feet" by John Vonhof.  Like I said I have both on my shelf if you don't want to purchase you can borrow.
Looking at what you have finished you will have no problem just keep on it going into the event.  If you visit the website run100s.com there are some example training programs listed there for the 50 mile distance and also the 100 just visit that as there is a ton of information there.  The only part that will make the Farmdale 50 tough will be doing loops, those are always hard to do, believe me I did 15 loops at McN for the 150, they are tough just get in an back out on the next especially when you see people dropping or going home or finishing a shorter distance, you think it is just not fair I want to be done.  You know how it goes, you did the 30 at McN.
Congrats on signing up.  That is the biggest step to throw your money down and make the commitment.  Now.... what will be your first 100? Kettle Moraine June of 1011  

Thanks to those already responding.  I know I made the right choice to sign up early, so I wouldn't back out later.  I'm plenty stubborn, ask my husband.  I've almost perfected this technique: not to listen to myself when the brain tells the legs to STOP.  I try and reverse that "tape" in my head and tell the legs they are STRONG and that it is my head that it is crazy....it has worked the past to marathons.
 
Mike, first weekend in June will be a half trail marathon with my husband in Deadwood SD.  This is his first half and I can't wait!!!  Kettle Moraine is great.  We ran trails there last fall in October.  Stayed in a great B & B in Plymouth.  I love following your accomplishments on the forum.  Please introduce yourself, if we cross paths.