Mini Tub Help

Hey guys, Me and my dad are thinking about mini tubbing my 70 dart. We understand we need to cut off the wheel well and we are going to insert a 3 inch piece of metal in the well in order to gain clearance all the way to the frame. But what we are not sure of is the spring relocation. Should we pay a professional to do it or can we do it ourselves. When you move the leaf spring mounting plate on the body does it have to be MIG welded or TIG welded? and also do the shocks need to be replaced with longer/shorter ones or can we use the existing? Lastly, if we do it by oursleves is thier a way to determine the proper angle of the that connects to the rear end? any help would be appreciated. thanks, rob