I attempted the glass-only replacement in spite of discouraging words from a more experienced tech. You will need either a hot plate or a very low power heat gun (the glue melts around 180F), you will need lots of plastic picks and scrapers. And if you wanna do it right, you will needs hours and a lot of patience.
If you attempt this, keep the glass mostly parallel to the screen at all times, go really slow, and apply enough heat. I was afraid of overheating the phone, and so the glue in the area i was pulling the glass off of had not fully melted. Well, the LCD is surprisingly scratch resistant, so that was not a problem, but it will still crack. And it did.
You can find a new digitizer for a little over $100. You can get a whole new phone for $200. And it will take you almost no time at all. I spent an entire day of straight work and ended up having the replace the phone anyway. Total cost was about $300 PLUS the time. SO: Unless you're a Kung-fu Master, just get the whole assembly.