For a skin mount you should keep the fish in as pristine condition as possible. Don't gut it and try to limit scale loss. A gutted fish can be repaired but it will cost you extra. Keep it cold and get it to your taxidermist ASAP. If you can't do that for a couple of days just put it in a large plastic bag, squeeze out as much air as you can, then freeze it. It will be fine like that for a couple of months.

For a reproduction, measure the length and girth (just in front of the dorsal fin), and take some close up photos. The more detail the photos show, the better the repro can be painted to match your individual specimen. If you don't have photos or exact measurements there are ways to get around that.

Repros are a good option, of course, but skin mounts can be done just as nice and can last too. They must be done right, though. Choose your taxidermist carefully. It's wise to do some checking around before you catch that big fish. The price quoted above of $12 per inch won't get you much these days.