Buy a shooter from someone who will "guarantee" it to shoot.
A matching pistol may work better than a mismatch, but many mismatched or assembled pistols work perfectly fine.
Lugers are not fragile, but like any firearm, parts can and do occasionally break.
If you intend to fire 1000's of rounds, I'd probably choose a "new" pistol, not one 75 or 100 years old.
