General :: Apps Don't Install / Want To Change OS

I received my nexus 4 from Ebay a couple of days ago. But it does not seem to work properly. Indeed, I do not have Google Play or the Voice Search on my nexus 4. I havemtried installing the app from the website Google Play. The website tells me I already have the apps installed. Every time I try to download a new app and try to install it, it just disappears after the download is completed. Meaning, I don't know where I freakin' goes. Since then I have spent a considerable amount of time (more than 15hours) browsing the web for solutions.

My Nexus 4 is running Android version 4.2.2 with CyanogenMod cm-10.1.2.

I don't want to use that OS, I want to use Kitkat or what ever works with Google Voice Search and consumes the least of my battery. I saw on the internet that SmoothLiquid seems to do that but at the moment I am so frustrated that I don't even want to try, I just want the average OS, with automatic updates. I have been on so many websites trying to understand how things work and trying to find solution to install a new OS but every time it gets really confusing. People talk about flash, root, ROM, OTA and PATH but this is just gibberish to me. I tried getting into it by reading a lot of things but it just doesn't make any sense. I don't know if I am supposed to enter commands from the Terminal (I only have a mac) or if the proposed unzipped files are supposed to be copied within the phone. I have installed Android File Transfer and I thought I could just copy past the image of an OS and install it from the phone but apparently no. I have even tried to install CWM 6.0.4.3 to prevent my phone from being broken before attempting any serious operation but I don't know how to do that. All the terms get really confusing so I'd rather do nothing than lose my investment. I though Androids and phones were supposed to be ready to use easy equipment of technology.