First - you'll need a good pair of binos. I've had outfitters using high end binos comment on the clarity and light gathering quality of my relatively inexpensive pair of Celestron 10X42s I picke up at skyoptics.com. If you have an outfitter, the guide should have a range finder and spotting scope. Your choice of caliber is great - the 270 will easily take a mulie at 300 yds plus. As for rifle support. I like the Versa-pod by Cabelas. It attaches and detatches easily so you don't need to have it on your rifle all the time. You can put it in your pack or belt holster. I recommend the longer one for shooting sitting/kneeling. I figure if you can get low enough to shoot prone, your pack will make a good solid rest.
If you can afford it (not knowing your financila situation) I would also recommend removing the Banner scope and getting some better glass. Something like a Burris Fullfield II with ballistic plex or a Leupold. A 3-9x by 40 is plenty of scope. Practice at 300 yds if you have the range.
By the way, I know the Burris BPlex works with the 270 shooting 130 gr bullets. I took a mulie and a ranged 437 yds. But I practiced out to 500 with my rifle all summer. Now I wouldn't shoot a deer at 500 yds and the 400+ shot was pushing my limitations. But I had a solid rest, no wind and a broadside shot. I just bracketed his chest between the 400 & 500 yds reticles and squeezed off the shot. The bullet entered mid heights behind the shoulder and exited out high on his left side - he rolled 50 yds down the mtn and laid stone dead.