ive uninstalled ldplayer myself, but from memory it was pre rooted. (you could download a rootchecker app from the playstore) but yes you will still need to download both busybox & luckypatcher. once you install the apk for busybox, open the app & click install. with lucky patcher, you need to install it then open, go to toolbox, patch to android, click the top 2 checkboxes, press apply, let it reset your device, open lucky patcher again, go to toolbox again, click the third box then apply. then after all that, you need to install the modded apk for injustice. follow this guide for that part.
Many people have problems to change the MOD version on NOX or to update the current version. Especially if they have the NOX rooted + Luckypatcher patched to be able to use unsigned MODs. If you want to use unsigned MODs too, follow this tutorial please: Tutorial - [Videotutorial] How To Login...