Answer to: Screen replacement screen onlyMost people are using the 3M double sided tape. If you look it up on EBay you'll see it. It's really thin and can be bought in thin pre cut strips.
Answer to: Screen replacement screen onlyVista LCD and digitizer are easy to replace. They aren't bonded together like many of the higher end phones. The screen is stuck to the frame with adhesive tape which is easily removed with the heat gun. The lcd is just laying in the frame below it. You must remove the back plate which is held on by screws, then remove camera modules, boards, etc so they won't be damaged when you heat it. Also you have to unplug the ribbon cables to remove the digitizer and LCD. All the components are modular and are easily replaced. I wouldn't hesitate to do it myself. Especially if you have done this type repair before.