Killed 2 deer with M1A, used Fed Premium 165grn. hunting rounds.
Suggest ya check out the ARMS #18 here:
www.armsmounts.com/list.html for your mount.
ARMS can also fix ya up w/ rings or Badger makes first class ones too.
As to processing, we always clean/gut the deer within 30 minutes. At the farm, ever how long it takes to go get the Kubota front-end loader and haul deer to cleaning area by old barn. At the lease I generally gut the deer on the ground where it lays, (it's realtively easy once ya get the technique down), then throw on back of 4 wheeler.
The quicker ya get the deer quartered and on ice the better for the meat. We normally leave the quartered deer in the ice chest for day or two, then process ourselves. Meat grinder is necessary and with different inserts it will make chili meat to sausage. Backstrap and loin are the choices parts and we like to size the portions and freeze whole, thaw then slice into 1/2" thk. sections, bread-batter then chicken-fry in the skillet, mmmm good.
Processing a med-sized deer from quartering to freezer is generally a 4-5 hour process unless there's lots of help, and don't forget the seasoning and pork necessary for creation of spicy (the way we like it) pan sausage.
Stock options are personal preference, but not necessary for hunting, recommend ya contact the Maine Fish & Wildlife dept. as they will have all the info ya need to get started, as well as covering all the local laws and lotteries for prime hunting sites. (guess they have those up there??)
While I shot my first deer at 8, your getting a late start, but what's the old saying, "better late than never", just remember, hunting is a serious responsibility and just because ya got a 5 or 20 round mag there, don't mean ya need to use it.
A good hunter makes clean kills w/ "one-shot", and this gets easier the more ya've hunted, as the first time that monster buck (or any deer which ya intend on takin for that matter) steps into the opening, "buck-fever" will have ya shaking in your boots.
Always shoot from a rested position if possible and don't forget to "breathe" and "squeeze".
Good luck and hunt responsibly,
Mike