It is usually not worth it, and there will be problems unless you can get the exact same screen as your broken one (same VCOM, compatible waveform). My Kobo Aura display replacement is fine, except text is not as crisp at times, and the frontlight is just not very good (remember Kindle Voyage frontlight issues? Same here).
Maybe another excuse to get a new eReader
tldr: don't unless it is for really cheap.