Welcome to PB. Smarter guys than myself will have some good advice for you, but here's mine for what it's worth.

I de-mucked and made deeper a much smaller pond using a 70hp 4x4 loader tractor.
It took me all of four summers working on it in my spare time.
I had a skeeter hole 300' from the pond where I could dump the spoil.

I can tell you right now that swinging the muck up onto the dam and then pushing it over is not going to work for long. That stuff takes forever to dry out unless you spread it out pretty thin and then it still takes forever to dry out. With all those trees behind the dam you don't have room anyway for the mountain of goo that needs to come out.

You won't be able to keep the hole dry enough to work in unless you cut the dam. Even with that done you'll still have to pump water out so you can work in it.

My project thread is here:
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=500175#Post500175

Most of the pics are missing thanks to tinypic shutting down, but I've gotten a few of them transferred to a new hosting site and a start on getting the pics back into the post. There are a few from the early work that will give you a bit of an idea what you're facing if you decide to clean out your pond.

Knowing what I know now, if I had another pond that I was determined to clean out, I'd call dirt guy and get ready to spend a lot of $$$.

Good luck with your project, however you decide to tackle it.