If this is the case, it shouldn’t be hard for you to use a bottle jack and some blocking to just jack up the timbers that this post is connected to, and slide the post back onto its correct spot.
Just make sure that the point where you're pushing up with the jack will lift everything and then just use a crow bar or something and push the post back where it should be. If the post doesn't rise up with the jack pushing up the upper part of the barn, then you might have more problems.
But to answer your first question, you could look in the resource guide for someone in your area that does restorations. You can find the resource guide link on the home page of the guild; it's on the top right hand side near the search button under online store. Then select restoration over the submit query box and using the pull down arrow select services, then click the submit query button. The resource guide will then show you 29 companies listed, and you can sort through them until you find one near your area. Good luck with your repairs. Jim