Here you go.

Yes. These are sturdy guns, and original Mauser parts were made of good materials. Ditto for Astras. (Other Spanish guns, and just about any Chinese gun, I can't say with reasonable certainty.) Some variants aren't fired much nowadays, but that's because they're expensive, not because they're fragile.

Yes. If yours is chambered in 9 mm, it will shoot any old 9x19 mm ammunition. That's the ordinary 9mm Luger, 9 mm Para, whatever. I'd avoid +P ammo, though - give the old lady a break, huh?

If the gun is chambered for the original Mauser 7.63 mm cartridge - most of them are - then you need 7.63 mm Mauser or 7.62x25 Tokarev ammo. Originally the two cartridges were identical. Nowadays some of the military surplus Tokarev is loaded a bit on the hot side. Whether that's a problem or not is a dynamic Internet discussion topic. See the Ammunition section for a long and tedious discussion of the question. Currently, new commercial (i.e., not surplus) Tokarev cartridges are made by Sellier & Bellot, and new Mauser cartridges are made by Fiocchi. The S&B seems a bit hot to me but some owners do fire it through their C-96s.

2024 UPDATE    The Mauser/Tokarev dichotomy is still an issue. See the Ammunition page for the latest and greatest.

A few new parts, such as springs, grip panels, and firing pins are available new, as are stripper clips, and of course old parts salvaged from original guns are sold by the usual suspects. See the Bibliography and Links page for some sources. Replacing the recoil spring and the mainspring is always a good idea. Normally the trigger spring and firing pin spring don't need to be replaced. The magazine spring - the big zigzag one - is prone to failure after a few decades of use, and if yours has broken, you can get a replacement.

The sight is a tangent type, as commonly seen on military rifles of the period. Don't try to flip it all the way up, it just won't go. Here it is at its maximum elevation -

The "New Safety" - on guns with an NS monogram on the back of the hammer - is operated by pulling the hammer back a bit past the full cock position. Then the safety lever can be pushed up and forward, engaging the safety. Excepting the earliest guns (with serials under 40000 or so), the other safety variants should work normally - back to fire, forward for safe. The early ones were opposite to that - forward to fire, back for safe. The whole story is here.

Don't neglect proper attire, and eye and ear protection.