Replacing sky router with ASUS XT9

[Astudystar12]

I have just moved back to the UK and have a Sky router. It's not full fibre and is FTTC until they upgrade the system. I bought an ASUS XT9 system when abroad and wondered if it is viable to either a) use it to replace the sky hub and plug direct into the broadband feed in the wall or b) connect it via Ethernet cable to the sky hub. 

Basically, we want to avoid WiFi dead spots in the house and enable a hard connection for gaming in one of the bedrooms.

I've seen conflicting posts and none seem to have an easy to follow step by step guide to replacing the Sky hub. Appreciate any help.