A complement to this guide: I purchased the replacement screen, but not the full frame. So I had to do the heat gun (*ahem* hair dryer) trick of heating up the edge of the frame to remove the screen (with the help of an X-acto knife and plastic spudger). Not difficult.
But upon reassembly, you absolutely must have adhesive to replace that which is lost around the frame, or a sticky sheet to put behind the screen, or the screen will simply fall out when the phone is inverted.
The part I ordered did include a transparent adhesive sheet to place behind the new screen and anchor it in space in the event that the edge adhesive was insufficient (even with more heat) to secure the screen. But as it was a chinese discount order, the part arrived with no instructions. I assumed the sheet was a bonus screen protector sheet. Imagine my surprise, after having fully reassembled the phone, to discover it's true purpose - which would require full disassembly to install...