The replacement of the glass only is a very very hard work and is nearly impossible without the right tools, machines and experience. The glass sticks together with the touchscreen. Removing it without any pretreatment will break the screen directly.
The worksteps are:
1. Heating up the LCD glass with a high temperature (not to high and not to less) so the glue begins to be fluent again
2. Removing the glass millimeter per millimeter while using a wire which you have to pull between the glass and touchscreen
3. Do steps 1. and 2. as long the glass is removed completely
4. Remove the last left broken glass-parts from the screen
5. Clean the screen from the glue-rests
6. Apply new glue on the touchscreen
7. Assemble the new glass
8. Dry the glue between glass and touchscreen with blacklight (UV-A)
9. Assemble the screen again
You see, there are a lot of steps to do, most of them are very difficult and you have a very high chance to break your screen on nearly every steps. Companies who make that professional have own machines for every single step to make a clean and preferably lossless work.
In other words: I would highly recommend to replace the whole LCD assembly (which is very expensive, yeah) or pay that high amount of money for the replacement if you really want to replace it. Maybe you can live with that little crack or sell the phone as it is for the best possible price as long it works that way.