It's a tight fit and I wouldn't recommend it. If fired, I would imagine the barrel getting stuck on the slide which would damage the outside of the barrel. I'd also be weary of what the recoil spring would act like.
No, only if you switch the entire slide. It can be used the other way around however. You can place a G19 barrel into a G32 pistol, and use 9mm, you would also have to use the G19 magazines.
It should be marked on the barrel.
$438 (new)
32
32
I would say that converting your Sigma 40 to 357 SIG would be straightforward however I doubt if the Glock barrel would drop in. I suggest that you contact Barstow. If anyone makes the barrel you want, it's them.
100-500 USD or so
Yes, the glock 23 and 32 and the 31 and 22 magazines are interchangeable.
in Florida
32--17-32 = 17
17% of 32 = 17% * 32 = 0.17 * 32 = 5.44
$32 a barrel