Changing to Plusnet Hub One

[#1]

After suffering some speed issues with wifi recently, Plusnet ran some tests and advised it may be my router at fault as everything else was coming back ok.  I wasn't impressed with the cost of the Hub One router through Plusnet and as my contract is up in July I was hoping I might of cut a deal to stay that included the Hub One with it.
Anyhow I have been able to get hold of a brand new Hub One from Ebay for under £15 including P&P and it has just arrived in the post   Can some one help me out with installation of this please?  Is it just a case of replacing the existing technicolout router with the Hub One, or do I need to do anything else?  Also do I still need the BT Openreach router that was installed as part of my Fibre broadband or do I take that out as well?
Thanks in advance

[#2]

You should be able to connect it up without using the Openreach modem, so it will replace both the technicolor router and the modem.
I'd recommend factory resetting the router first and then log in to it at 192.168.1.254, then click settings. You'll be asked for a password which should be on the card/on the base of the router. Following this, select the 'broadband' tab or click 'enter your broadband username and password' you may need to click disconnect to enter your details (username@plusdsl.net and your password) and then click connect.
Please could you also PM me the serial number of the router so I can make sure it's not connected to someone else's account. Thanks.

[#3]

I have sent you a pm with serial number and other questions, also I now have wifi up and running but still can't alter the settings or select any of the tabs on the router home page.
Thanks for all your help