Manual says " 5W30 not recommended for sustained high speed driving."

The kicker is quantifying high speed, to me it's cruising 90 ~ 100 (and above) for long periods, then again your outside ambient temperature is an important variable.

I agree. sustained 70 mph cross country with an occasional spurt would be fine.

Changing (or carrying spare) belts and hoses idea is great, especially the hoses, I'd also include a couple quarts of oil and a few wrenches. I'd also program my cell for AAA or whatever emermency road service you may use. For some strange reason mechanical failures don't occur in the parking lot of Auto Zone or Pep Boys.

I once changed a water pump in Wyoming in the middle of winter, and was damn glad to have found a rebuilt right one before they closed down the town for the night. Talk about cold.

Remember, when changing belts, don't over tighten the tension, this causes unnecessary stress and premature failure of the bearings (I've seen supposed qualified mechanics do this).

Have a safe trip.