I am the Vice President of a riding club and we hold Western shows. Braiding is frowned on for western classes - I know it sucks - stick to banding it or just making sure it is clean and tidy but natural. I am also a paint owner. She is black and white so I have the worst of all worlds when it comes to keeping her clean.
You need to make sure that your stallion is still going to be docile when he encounters other horses at the show - sometimes there are mares in heat there. You probably would do well just taking him to a show without expectations of showing the very first time, just to make sure he is not going to act up, plus this gets him accustomed to all the sights, sounds, and smells of what is going on at the show.
You want your horse to be as well behaved as possible so start working on the ground with him. Make sure he leads like a dream at a walk and a trot. Make sure he backs up as well as he moves forward.You also need to teach him to square up his feet and stand still. Join a riding club that offers points, trophies & ribbons. Every class you win adds value to your horse. I use two products for every show to keep my paints white parts white, showclean which is a whitening shampoo...and then a spray on stain remover that requires no rinse. I find that you need to groom your horse everyday to give it the really cared for look, not just the day before a show...do it everyday and it will stimulate the skin to produce a really shiny coat (not the kind you spray on)...feed your horse as well as you can possibly feed - inner health = outer beauty.
I would suggest you do Halter Class, Showmanship, and the Trail Class to start out with. Adult Walk Trot is also a good choice for the beginner. Western Pleasure is a little trickier because you have to have a nice collected canter to pull this one off. My horse has too long of a stride (at least this year we are working on it) to complete Western Pleasure class without running down the rest of the riders.
To me shows are so much fun, showing off how wonderful your horse is. If you are looking to stud out your horse it will also be an opportunity to meet people who may want your stud's services and prove he is beautiful as well as well rounded. Good Luck!