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 poor ol' thing 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 [Sorry - dead at the moment.] . The mainspring can get a bit tired, but it's not urgent to replace it, as nothing evil happens if it's too weak. The recoil spring is another matter. If it's obviously too short, it would probably be a good idea to replace it, to minimize chances of battering of the bolt stop. Normally the trigger spring and firing pin spring are fine and there's no point in replacing them. The magazine spring - the big zigzag one - sometimes breaks at the zigs after a few decades of use. Replacments are available (at least they were the last time I looked), though the shaping of the steel at the ends may not be quite right, possibly requiring a little touchup with a grinder.

Some owners replace the bolt stop with a new repro. Someone was making these at one time; I have no idea if they're available now. The reasoning behind replacment is that the stop is the only thing preventing the bolt from flying out the back of the gun, and if it fractures things could get exciting. I've never found replacement necessary, and am not entirely convinced that it would be a good idea. My reasoning is that the quality of the metal in Mauser-made original parts is very high, as is pretty obvious if they've lasted until now; on the other hand, we have no idea who makes the replacement parts, and quality is a great unknown. I put my trust in Mauser; your mileage may vary. If, however, the barrel extension has cracked behind the bolt stop due to years of battering, don't attempt to shoot it, and don't attempt to repair it - just retire it.

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.