I made the large 3D bear for my SIL's baby shower. It was my first time too. It went better than I had anticipated. I used a dense pound cake, chocolate chip to be exact, and filled it up with the recommended amount of batter (6 cups plus 2/3 cup for the core). It ended up not being full enough (I had plenty leftover dough, but though it would be a waste and wanted to use it up in something else... ). But no one noticed that it was slightly short in the legs
My brother did pinch the edges closed with pliers. He's so handy. I swear I had no spillage at all!
I had no problem with the head coming off. It was really stable, probably becuase of the type of cake. And no crumbs! Made icing it that much easier
I did find it hard to center the core back into the cake. After it baked, I noticed it was too close to the front of the body, and ripped a little hole when trying to remove the core. But other than that, for a first time try at any 3D type cake, it went really, really well.
I had to trust myself! And remember, icing can fix A LOT!
P.S. Here's the recipe for the pound cake. http://www.robinhood.ca/recipe.details.asp?prcid=11&rid=7
P.S.S. Welcome to CC!