You might be wise to take out the trailer dividers in case tying to the
trailer doesn't work out and you have to go to plan B (example - other
people's loose horses keep running around your trailer all night - it
happens. I made a portable corral out of tubular steel gates from Southern
States. It was cheaper than a ready made corral and has rails spaced close
together - no room for horse heads to poke thru. Stay away from electric
fence, JMO but I don't trust it.
About the conditioning, read different books/articles, find out your horse's
history - how many years of what kind of riding/old injuries.
I started in '97 and can't believe how little I knew then and how green I
still am. Good luck.