You wrote:
> Where would I start to get myself in shape for endurance, I assume you have
> to be in good shape to do this?
It sure helps you & the horse!
1) Take lessons (dressage or centered riding (fancy name for dressage 
for trailriders)) 
2)  Ride
3)  Walk a lot
4)  Ride even more
5)  Run or jog
6)  Ride more yet
Are you seeing a trend?  Some of what we do is aerobic work (tailing, 
jogging w/ horse, etc.) and some is riding skill and endurance of 
your "riding muscles".  You need to develop all of these.  You know 
you are making headway when your friends say you ride too far, too 
fast, for too long, and that you look <fabulous> in your bathing suit 
(except for those scars on your legs and callouses on your seat).
Linda Flemmer 
ABF Challenger ("Rocket") & Eternal Point ("Major")
Blue Wolf Ranch   Chesapeake, Virginia, USA
   "In case of emergency - Fur side up, steel side down!"