Forrest61,
First, there is absolutely no need to shoot in uncompressed raw on the D700. Change the settings to "lossless compressed", and your raw files will only be about 14 MB each. You'll be able to fit more shots on each card, the images will download faster, and you'll save on disk space. The resulting images are mathematically identical to an uncompressed raw.
Yes, a DNG places the 12-bit or 14-bit data into a 16-bit container, so no data is discarded when you do a lossless conversion. It is only when you opt to use lossy compression or downsize the image when some data obviously needs to be thrown out.
Once the image is opened in Photoshop, it will not show whether the source was 12-bit or 14-bit. Photoshop documents exist as 8-bit, 16-bit or 32-bit documents. There are no in-between bit depths, since they operate in multiples of 8 (8 bits in a byte). So whether you open a 12-bit or a 14-bit NEF, they will appear in Photoshop as either 8-bit or 16-bit documents, depending on your settings.
