The digitizer is fused together with the LCD. That's how flagship phones are now these days for years.
The glass is just a piece of glass. Getting the right loca liquid glue or some similar adhesive is the way to do it and the hard part is keeping out the dust and making it spot less clean so that it looks good.
I always leave it to the experienced professional screen refurbishers and replace the screen (Seriously these LCDs are pretty fragile). If the touch screen is very easy to separate from the LCD like cheaper phones are I would replace separately.