Pasting a selection from one layer into another

Is there anyway to paste a selection from one layer into another existing layer (Not creating new layer)? Or, by extension, is there anyway to merge one layer into a current layer that has a Layer Style applied to.
What I am trying to achieve is to be able to add information into a layer which has a Layer Style by cutting/pasting/merging information from another layer; I wish to retain the Layer Style adjustibility.

Place the layer with the new data directly above the layer that has the layer style. Make the upper layer your active layer and then choose layer/merge down. This will add the new data to the lower layer while maintaing your layer style.

If you want to maintain the layers seperate, apply your styles to the first layer, then right click on the little style icon in the layer in the layers pallet.
Choose copy style, then drop down to the other layer, and right click again. Paste style.