Glueing in batteries and inventing their own proprietary screws clearly show Apple does not want anyone else fixing their products. I've personally had bad experiences in their stores and have heard horror stories. Not to say there are not unethical 3rd party repair shops but that is the best way to go.
Apple has even threatened legal action against third party companies that publish repair schematics for their products. They have previously done some nasty stuff without disclosing to their customers. The most egregious was probably when they admitted to slowing down performance of older iPhones.