Buy one.
What gun?
yes
New Mexico's gun laws are pretty lenient. New Mexico does not require a hand gun to be licensed or registered.
That will depend on the seller of the gun. If it was a new gun, they could no longer sell it as new, so do not expect a full refund. If there is a defect in the gun, some sellers will take it back, fix it, or refer you to the maker of the gun for warranty service.
only at "gun shows"
Anywhere it is legal. Your local police and gun shop can help you.
mp45 is a new gun
No,
My New Gun - 1992 is rated/received certificates of: Australia:M UK:15 USA:R
gun shop, gun show.
Numrich (In New York)
No.