If you are in a position that you can leave the bird intact and freeze the entire carcass (or keep it on ice), that is the very best thing to do. However, there are often times when that is not going to be feasible. If not, here is what I suggest:
1) If your future plans are to have a number of birds mounted, learn how to cape them. It is not nearly as difficult as people seem to think it is,...and it makes dealing with birds that you want to mount sooo much easier. You also never have to sacrifice the meat of the bird, which should always be a primary consideration.
2) If you don't want to learn to cape a turkey, be aware that you will have a lot more trouble keeping one in good shape for a taxidermist (or eating) under most hunting conditions than you will by simply learning to do the caping process yourself.
3) If you still don't want to learn to cape your own birds, you can still gut/field dress the bird. Just go through the normal gutting process of making an incision at or above the vent, and pulling all the "innards" out.
4) Stop thinking you need to annihilate a turkeys head and neck by shooting the most concentrated shot pattern you possibly can. One of the biggest issues with a good turkey mount is the destruction done by highly concentrated shot patterns in the feathers below the neck,...or by a body shot bird. For mounting purposes, use a reliable, good-patterning shotgun,...and don't try to blow the turkeys head off.
5) If you shoot a great bird, but question whether you damaged it beyond mounting, be aware that a good taxidermist can repair just about any kind of damage you could do to a bird,...within reason. If your birds loses many of the major "display feathers" (tail feathers, wing feathers) pick those up and keep them for the taxidermist. Take care not to carelessly damage/bend/break feathers on your bird.
6) Regardless of all else, you cannot let the bird/cape spoil before getting it to any taxidermist. Keeping it frozen/very cold as soon after it is killed,...and not allowing it to get warm/hot for any length of time, is critical.
7) The trophy characteristics of a gobbler are generally thought of to be the beard and spurs. If you want a full mount of any bird that you killed,...even years ago,...of which you still have the beard and spurs intact, you can always use a replacement cape for a mount. All is never lost....
