shot placement is everything. so yes yer 243 will work fine if your a good shot.
the brake on the other gun is what takes the kick away. you can have one added to any gun when ever ya want.
as mentioned it wont be 600 pounds of meat. a good atv can help with this if ya had one. they make some pretty cool compact sleds ya drag behind you when ya fold it out, and it beats putting it all on your back and hiking it out multiple times.
as far as physical capabilities, only you will know. sounds like you will be fine from reading your post.
just gut it in the field. leaves alot of weight.
some people quarter em up to fit everything on the sled better. i believe in cutting em up after the rigor lets go. to each their own.
fyi might be a good idea to hunt up hill, easier to drag em down hill
gl