Jim, if you're certain it's red sandstone, feel free to carve on it. But if it came from an old building, it might possibly be unpolished Minnesota Red.

Minnesota Red is a type of granite that was used on buildings, for gravestones, and so on early in the 20th Century. But like its companion granite, Minnesota Black, the quarries gave out. As a result, even a small piece is worth quite a bit of money -- no new granite means that you can't match the stones in Ye Olde Family Burying Plot unless you use recycled granite. Therefore, matching the stones means paying through the nose.

If I were you, I'd hie myself down to the public library and check out a book on stonecarving. Then fool around with scrap stone so you can get the feel of the tools, etc. before you start "for real."

Good quality sandpapers will serve well as final buffers. You needn't try to polish it (and if it's sandstone, you can't do much of a polish job anyway).