I know a teensy, little bit about Xmas trees, because the cabin I'm selling is located in Ashe County, North Carolina, the Fraser Fir Xmas Tree capital of the country. The first thing I know is that you probably won't be able to grow Fraser Firs; like wine grapes, they seem to like certain elevations and temperature variations, and Northwest North Carolina is pretty close to being ideal.
I also went to college for my first two years in central Pennsylvnia, which claims to be the Xmas Tree capital of the country for almost all other varieties other than Fraser Fir; primarily White Pine.
In Ashe County, NC, everyone who has an acre or more is involved in growing trees. School teachers, bank managers, hardware store owners and just about everyone else takes their vacation in the weeks prior to Thanksgiving to cut and bale the trees. Any space that has enough room for semi-trailers to turn around has a staging area for the trees. Small farmers roll into town with trees tied to a trailer and their pickup truck, dozens of trees precariously balanced and weighing them down almost to the ground. It's an
enormous industry, and almost always lucrative.
I also learned quite a bit about it because for years, I rented a Ryder truck and bought a truckload of trees to bring back to Florida and sell. I bought my trees from the bank manager and his brother.
You'll have to research which varieties are possible to grow in your area, and which of those are most valuable. As bczoom mentioned, spacing is important, and placing the new tree next to the stump of the old is exactly what they do. Other than occasional mowing and some fertilizing in the early days, the greatest effort is required for trimming. I don't know the frequency, but high school and college kids work the fields as summer jobs, pruning and shaping the trees for the greatest value. Back in the day when I was selling the trees, perhaps 10 years ago, the kids were getting something like 25 cents per tree.
Because of the location of the field, you would probably want to spend a little more time mowing and weeding to keep the field looking attractive. You should need any additional equipment, although you might check to see if a tree shear would be effective and not damage the tree. Otherwise, you'll need several good chain saws. They cut as close to the ground as possible. You'll also most likely need a bailing machine, although it's possible you might find a single buyer who will come through and bale and load your trees on his trucks.
Most of the trees I saw being harvested in Ashe County came out through someone's yard, so that shouldn't be a problem. A rugged trailer to pull behind your tractor should get them out; your NH could pull the baler through the field.
Timing will depend on the variety you grow, but generally it takes 6 to 10 years, depending on variety and size, to get your first return. The trick is to plant only 10% of your field the first year, then add another 10% each year until you have the whole thing on a rotation. Figure maybe 3 acres per year, with the extra 2 acres (or 32) spread around for access. I forget how many trees you can get per acre, but it's a right decent number, 1500 to 2000 if I recall correctly. That could give you 4000 to 6000 trees per year to harvest...
For marketing, the "cut it yourself" approach is out for you, but depending on the quality of your trees, there are a couple of other approaches. Research and find the folks who market to the big box stores and sell your entire crop, sight unseen, for a lower price. Or, make contact with the folks in your area who sell directly to the public, and market directly to them. In our area, that ranges from individual Rotary Clubs and small retailers with one location like I was, up to large retailers with chains of locations.
The toughest thing I can see, providing there is a marketable vaierty that will grow in your area, is locating the folks who know what they're doing and are willing to share with you.