I don't know very much about business, but I do know about money. Congrats on buying property by the way. I would say that your best bet is to build the domes first, sell them, then buy more land.
This way if any thing should befall you or your endeavor you won't have a loan looming over your head. Just remember; the borrower is servant to the lender, don't borrow money unless you must.
If you happen upon a deal where you can buy the land and finish out all your domes, without a loan, by all means do so.
As for your GM, trash him. Politely. If you find any one questionable you should know in your gut he's no good. I've heard plenty of stories about shady contractors that take the money, do a little bit of work and then leave, without so much as a forwarding address.
Be sure to fire him politely though, you want to stay good with people, if your gut is wrong.
I suggest you use locals, start with the people. New Orleans people are good people, they'll tell you who's good and who isn't. Look especially at finished houses in otherwise shabby neighborhoods. Go up to the door. Introduce your self by your first name, tell them what you are doing. Ask them for their time. Find out who they used, chances are they are still around.
Remember; be with wise men and become wise. Be with fools and become foolish.
As for your experience, you need to start somewhere, this is the place.
Also, if you have any free time their is tons of experience to be had all over the city, volunteer your time to the people who are living there. Or you can take a trip to the home improvement super store and spend a few hundred dollars on books, learn vicariously though the authors and gain a better understanding of materials and techniques.
Don't give up, Don't give up, DON'T GIVE UP.
Best of Luck