First time custom rom

Alright so I have been wanting to change my htc one (802w/dual sim) from android 5.0.2, back to 4.4.2 or 4.4.3 though I want a full stock/htc like software of the android version.

I found some here http://forum.xda-developers.com/show....php?t=2617159
I've got a few questions though as I am a bit afraid I might harm my phone (saw some posts that some phones might break down and not function again..)

First thing about the RUU and firmware, I figured some stuff but please correct me if I'm wrong:
I will be downloading Android 4.2.2 RUU version: 2.19.401.1 - then OTA update version: 2.41.401.1-2.19.401.1 (should be still android 4.2.2 according to the collection thread)
And to be able to get to android 4.4.2 (might not need 4.4.3) I will download OTA 4.21.401.5-2.41.401.1

Well, is there anything wrong with the OTA versions or RUU?
Also, when I get to Android 4.2.2, can I just mainly check for updates over "Software updates" and will I get the updates from HTC? Or they will prevent it as I installed a *custom* rom?

And for the main thing, please link me any tutorial or guide (in-depth will be appreciated.. would like to know what I'm doing) to install the rom and any other files if needed.

Sorry for the long post, have a good day!

Regards,
Matt.