[Q] Root Moto G 2013 and warranty topic

I have a brand new moto G (2013 lte) and I'd like to root it and install custom Roms. I read some articles in internet and I read that if you want to unlock the bootloader you need a code you get from Motorola's website. Requesting the code code will void your warranty because your phone will be saved by Motorola as unlocked. But I also read articles where they use Cf auto root (by chain fire) to automatically root the moto g and there is no sign to request the Motorola unlock code in any step. Must the phone be already unlocked before cf autoroot or there is a way to root without being saved in Motorola databases? There is a way to unroot? I purchased the moto g from amazon, and I think that if I brick my phone rooting and I don't tell amazon that I tried to root, they would replace my phone anyway. I'm scared of the Motorola databases instead. I'm asking so because I own a nexus 5 and I rooted it, then I had to send in back because of a screen problem, so I unroofed and everything went very well. Thank you and sorry for horrible English.