There are A LOT "it depends" going on here and a site visit by a professional would advised, but I understand the expense involved so...

Keep in mind that I have little to no experience in pond building or the reverse.

Assuming that it is not a water table pond...

Any time you take a hole that holds water and fill it in, you run the risk of creating a very wet swampy area. I would at least consider creating a gravel vein (french drain) from the very bottom of the pond through the dam that extends to a point where it can daylight or at least meet porous earth. This way any water that collects in the earth that has been used to fill the pond can drain out. And, make sure your fill has some drainage ability (filling it back up with clay would defeat the french drain).

If it's a tradition dammed pond, you could cut the dam where the natural course of running water would "like" to flow and use the dam materials to fill in the very bottom and lessen the side slopes. This leaves the ravine/ditch that it was originally created in. Of course, if your wanting a plateau as a result, you'll have to bring in dirt and consider the french drain.

Welcome to the forums!

Fish on!,
Noel