So here is a follow-up, posted in the hope that someone as ignorant as I will in the future search this forum and find this message and learn from my mistakes. As you all know, I really wanted to do this project myself, but in the end, was "convinced" by the powers that be that this would have been a foolish and wasteful endeavor. As it turned out, hiring a "pro" was foolish and wasteful endeavor.
In retrospect, I made quite a few serious errors in the way I handled hiring this job out. For starters, I relied on word-of-mouth, which is generally preferable to merely selecting someone based on who has the biggest ad in the yellow pages. My dozer man came highly regarded from a contractor whose work for me I had been pleased with, so I expected that this guy would be good.
The dozer man estimated it would take him about 50 hours at $125/hr, so I budgeted about $6K for the project. I should have know full well right then that hiring this job out by the hour was just volunteering to buy the guy a new dozer. As things turned out, he burnt through the $6K and got maybe 1/3 of the way done, but I'm getting ahead of myself here.
My advice to those who want to hire this sort of thing out is as follows. Get estimates from several contractors and make certain that they are firm-fixed quotes, not by the hour, and make sure they are in writing and make sure they are signed off by both parties prior to beginning the project. That way, the contractor is motivated to estimate accurately because he's only getting paid one amount regardless of how many hours it takes him to do the job. My mistake was simply accepting the verbal low-ball estimate and verbally agreeing to the job. As a result, I wasted $6K to get a job less than half done.
Another alarm that should have gone off was when the guy showed up with a D5. I might have bought a D5-class dozer had I done the job myself, simply because I wouldn't care how long it took me. But when I am paying someone by the hour, I very much care how long it will take. This project really needed a D6 or larger dozer, but more than that, it really needed someone who knew earth moving well enough to know what the right tool for the job was (which would probably be a giant motor scraper).
In the end, I kicked the guy out after eating up my $6K, and now I'm stuck with a mess. The dam is about 3' shorter than it used to be, and the pond basin is now about 2/3 as large as it used to be, but the net result is that I still have a pond and a dam, both of which need to be removed and replaced with level ground.
So I'm not sure what I'm going to do next, but I guess I learned a thing or two. My mom always told me that education is the most expensive part of life. I just hope this post helps those that find themselves in a similar situation in the future. Don't repeat the mistakes I made.