First off, if you have two Trijicon scopes you've been using with success, then take one (or both) of those. Sight the spare scope in, toss it in your bag, then mount the other scope, sight it in and you are good to go. If the one on the gun craps out, you can put the other on and keep going.
I will toss this out there though - simple and light are great benefits when climbing the rocks for sheep. I'd suggest a FIXED power (6X) Leupold for your trip (the FX-3 6X42mm, specifically.)
I know that is SACRILEGE on this forum. But at 600 yards, the animal will appear as if 'only' at 100 yards. I'm pretty sure your 55 year old eyes can see and hit something at 100 yards, so the fixed 6X scope will do the trick nicely. Besides, the scope is NOT meant for 'glassing'. When you point your gun at people, they don't like it. That's what your binoculars will be for. The scope is just for SHOOTING and the 6X will be fine for that. Besides, weight is only 13.6 ounces. Light is right!
Just had to toss this 'idea' into the ring. Let the flaming begin