I currently have the opportunity to buy a nice pair of name brand 12*50 binoculars for cheap. I currently use 10*42 Nikon's. I am a little concerned about the magnification and if they will need to be used on a tripod or if I am over thinking it? just thinking that is pretty powerful.

I'd buy them. If they don't work, sell then. I've got 10x50 and wish I had 12's

Whether you need an aid to steady them depends. Good ergonomics and well balanced binocs can help a lot. The heavier they are the more difficult they will be to steady. Extended glassing amplifies that effect. Some individuals are naturally more steady and can steady 12x binocs just fine. For most the limit is somewhere from 8x-10x. For me at age 58 the limit is well balanced 10x. Larger objective binocs with high magnification are bouncy in my hands these days and that stinks. I really like 50mm objective binocs but these days when I look through them I turn into old shaky Jim. If the price is right and it is not a financial hardship if they are a bust I would give them a try. If they work for you, you will gain the advantage of better visibility. For it to work for you though, you are beating the odds. For me to gain visibility comes at the added expense of higher end glass with better resolution.
Sorry for the rambling response. Hope you can pick something useful out of it.

Appreciate the feedback. I did jump on the purchase and will see how it turns out.