My advice would be not to stress over everything. So many people with their first horse freak out at the smallest scratch, or if they don't have every rug in the world on when it rains. Horses are pretty tough animals, while you should have the vets details, don't be to hasty to get one out. I've had horses for eight years and never had a vet out (knock on wood).
Listen to all advice, but don't act on it blindly. Their are lots of very knowledgeable people in the horse world, but just because they are experienced doesn't mean their way is best or even suitable for you and your horse. Remember your horse has feelings, and most of the time they just don't understand, lots of people get impatient, I get impatient, and they want to use whips and ropes in the wrong way and the horse ends up scared. The gentler way takes longer sometimes, but its worth it.
I don't think my advice is great though.
Don't put brushing boots on upside down, wide bits at the bottom, flaps pointing back.
Don't hold the rug up like a sheet and walk to towards the horse when putting it on for the first time.
Tie with the quick release knot.
They are all things I wish people would have told me before I got my first horse so I didn't look like a twit with upside down boots and my horse on the other side of the yard while I stood their holding the rug and looking at my only lead rope, now broken.