Depending on the tools you own and experience you have on doing Glass Only replacements on the Samsung Galaxy models (I assume not much from your question)... I would urge you to do the Whole assembly. If you do the glass only, it takes quite a bit of skill and experience to remove the glass without breaking your LCD. And even if you are lucky enough to get the glass off, cleaning the OCA glue is a rather difficult process as well. IF you manage both of these things successfully, you still have the hard part of applying New OCA or LOCA glue to apply the new glass and it is extremely difficult to without getting the glue inside the Backlight/under the LCD and botching the whole job.
Samsung is proud of their LCD's and it shows in the price, but you would be best served in paying a bit more for the assembly and doing without the headach and heart break of a glass only repair.
If you need any more information and decide to move forward with the Glass only anyway, feel free to repost any questions and I'd be happy to answer. Sometimes, it is even cheaper to just find another good deal on a used phone than to buy the new LCD.
Best of Luck!