Always seemed a good idea to me to carry 2 spares (required in the Grand), especially for remote trips. Watched someone break ALL their oars on the Dolores back in the late 70's, those were the days when used hose clamps and splints to get to camp, then glassed back together overnight... (wood oars, pre-Carlisle and Cataract and even Sawyer composites, although Smokers were just becoming popular).
You won't need any special tip/blade/end unless you stick to a cobble bar (rocky bottom) and manage to put the tip between rocks. I've had to pole raft and flotilla of rafts off sand bars on the Green and Colorado, usually find it's the spin-o-rama move that works best. A 10 or 11 foot oar is way more than necessary, canoe paddle usually works best (someone else's best of all, obviously...) - but in the end, you may find "someone" has to go overboard and lift/push/pull/curse. The colder the water and air temp, the more difficult to recruit "someone." If you're alone, just get it over with...