Have you ever changed a motorcycle clutch before or have a friend how has...... If not plan for it to be a multi weekend project. That Said.. If you have a manual and can follow instructions, have a helper and are reasonably familiar with the difference in open and box end wrenches. You can do a clutch in a Saturday and ride Sunday, if not Saturday night.
Not sure on the Shadow but I did it on my Rebel and as long as you do your homework up front it's not that difficult. Just make sure you do it all in the same day otherwise you may forget how things go back together. Soak the new plates for a day or two in fresh oil. And get a book or this may help(I use both).Honda VT750DC Shop Manual
It is very easy, but you will have to drop the exhaust, so be sure to get 2 new exhaust gaskets. You may also want to get a clutch basket wrench. This would be a good time to upgrade the springs. I did mine and it was a big difference.
Your clutch will generally start slipping in 5th then down from there that will tell you it's time. The motor will rev and fell like you have no power. When you pull the basket and pull the steel plates,you can lay them on a piece of glass to see if they are warped. If not clean them up lightly with a green pad. Don't forget to soak your friction plates for a day or 2 or you won't get the full life out of them.