Nugent has a ton of videos on the RA-TECH one.
<YOU WILL NEED TO MOD SOMETHINGS, minor though>
I just installed mine not to long ago, love it, can never go back to OEM.
It's more RS spec, takes RS dust cover, grips no modding required.. trigger guard still needs some fitment.
Biggest one would be it accepts real steel barrel nuts.
They aren't cheap, but if you're on a budget, B2 had them in stock for $70+shipping+tax (Blank lowers)
Any more questions best you just go to the fb group for ghk owners.
https://www.facebook.com/groups/G.H.K.owners/