Glad to hear from another Mainer out there. I'll share some things I've come across. There are many threads on hear that talk about hard starting in cold weather, if you do a search you should find plenty of info. The most common problems with cool starting are the glow plug relay going bad and the glow plugs themselves failing. The Glow Plug Relay (GPR) is fairly simple to trouble shoot
Here is an ok explanation of the GP system on our trucks from another forum.
Hard/No Start? Check here first. - TheDieselStop.com Forums
Here is an explanation of the Glow Plug Control Module, installed on california emissions vehicles, most likely you truck doesn't have this system but it might, mine does.
How to Diagnose the Ford Glow Plug
The glow plug relay in on the passenger side of the motor just back from the "powerstroke" cover, it is the relay all the way back toward the firewall. The second relay is for the Intake Air Heater (IAH). The intake air heater comes on based on oil temp, air temp (anything below 32 degrees) and one more parameter I'm not sure of. The IAH does not directly aid in starting but once the motor is running it helps to heat up the intake air charge and prevents white smoke and generally helps the engine run in the cold.
My truck was also starting hard in the cold, it would always start at anything under ten degrees but always had to crank it alot. Come to find out the AIH relay was bad, replaced that, didn't help a heck of alot.
But the biggest thing I did that helps was changed to 5W-40 Rotella T sythetic, it was night and day how much faster the engine cranks and how much smoother the engine idles in the cold. If you oil is near a change this is work a try as well as checking the GP system. I don't have a place where I can plug my truck in so I always have to start it cold unfortunately. I was using 15W-40 Rotella up until a few days ago, but I'm confident that my truck will fire right up with the 5W-40 in it in the negatives. It's been consistently firing right up at 5-10 degrees. The down side is it's about 16 dollars a gallon for the stuff and the only place you will probably find it in Maine is at Wal-Mart, very pricey. . Hope this helps.