You'll more then likely need a lawyer like you said for the land transfer and surveying and the township would need to be involved also. There are usually size restrictions also that need to be met when dividing lots like that.

For the building play it safe and get an attorney and the township to deal with it. It usually also depends on what the building is to be used for. My property was separated from my neighbors years before I bought it and my building doesn't have the proper clearances to be used for livestock so there is a clause on the title stating that it won't be used for that purpose. SInce it's an existing structure you might run into something like that to make the distance to the property line work.