First of all, I would go ahead with getting him neutered. Only because it is healthier for him. I don't believe it will cut down on the barking any.

Second of all.....does your sheltie like food? That may seem like a silly question, but I have heard of the odd picky sheltie out there. I don't know if they are urban legend or not though....LOL

This is how I would go about training your sheltie to stop barking, especially if you want to avoid the water route (never worked with my shelties, they would just run out of range and keep barking....LOL). Get your dog's absolute most favorite treats and keep them with you all the time. When something sets the dog off, grab the treats walk up to your dog and put a treat right in front of his nose. This will distract him and you can give him what will be his command (ie Quiet, Shush, No Bark, Enough......etc) lead him away a few steps (to remove him from the situation) and then give him the treat.
What you are doing is creating a conditioned reinforcer where the word = food. This won't prevent your dog from barking, but it will allow you to get control. The only thing that will prevent your dog from barking is to remove any and all stimuli in the environment and well that's impossible.
You can also strengthen the word you use by taking your dog into a quiet room and just saying the word and giving a treat. The dog doesn't have to be barking in order to do this.

Your end goal is to be able to give the command when he is in full bark mode and have him come running to you for his treat.

I hope I explained that properly. Let me know if there's any part you don't understand and I'll try to clarify.