We just picked up a gelding and a mare who have been out in the pasture for a couple of years with very little work. They are very attached, when we take one away from the other for work - they both get agitated and vocal.

We've taken the gelding into a stall to break the bond and help him bond to us. It's only been a few days and he seems to be getting better adjusted, but he definitely doesn't like the stall. He also needs training. Is now the best time to send him out? Is there any other things we can be doing to get him comfortable with us and not so dependent on the other horse?

Think like a horse.
They are currently a herd of 2- You need to become part of the herd, and not only part of it-the Leader
There are books a videos-I personally don't like most of them so reluctant to recommend any.
Only because they give a;
You do A - Horse will do B
Not really horse will most likely do Q- problem is that senerio isn't in the book.

For instance-When you feed him.
You put the feed in a walk away, thinking it all right buddy you can eat.
He thinks-thats right you had better be gone before I get there.

Learn body stances-
If you puff your chest up and take a deep breath in, hold your hand open-to a horse that is a sign of domenance and they should back away from you. Trying to catch a hard to catch horse, the more they run the tenser/madder you get-the more they run-see above.

If you take a deep breath out slump your shoulders, hand loose fist not looking directly at horse, chances are alot better that they will be caught.


Trainers-
Find a good one alot of damage can be done in the wrong hands.
Visit the farm both planned and unexpected
Ask around town-feed stores/Vets/Farriers/other riders
Look @ condition of horses and stalls/fields/arena
Look @ horses interaction with people are they stand offish or eager for attention
Look @ tack, although horses are big they don't need medevil looking equipment
Horses don't get bucked out anymore- thats only in cowboy movies-training done correctly should produce no unwanted side effects.
No bucking/rearing/fear, etc..
If @ any point it does, it is being done wrong.

Do try to rotate who's in and who's out, unless you really can't catch one.
If they are used to being out 24/7 they will go crazy being in.
Yes sending off for training is a good idea- remember to write down daily routines.
Otherwise no matter how good the training was they will revert back to a herd of two and all you did was waste money.

Welcome to the world of horses.