Hope you're ready for this....
Wire up and log in using the URL 192.168.1.254 and the default username and password is admin admin (case sensitive)
Click on Quick Start (

) and you will be able to change any of the details to which were in your old router such as Authentication Protocol etc and you can opt to change the DNS from ISP default (make a note of it first) to something like Google 8.8.8.8 / 8.8.4.4 if you want.
The MTU on mine was default set to 1492, but for TalkTalk, they recommend 1432 and Plusnet may have their own preference, but the optimum is whatever you've found to be best (as you'll know).
Enabling IPv6 is optional and unless your ISP supports it, then it's best left unticked as enabling it can cause connectivity problems.
Click on Continue and wait for the router to configure the settings - it will tell you whether that has been successful or not and if it isn't, then reboot and start again.
Click on Jump to wireless settings and this is where you can name your SSID to whatever you wish > change/leave the channel and as you know WEP isn't ideal and trying at least, just WPA would be an improvement.
Type in the SSID's shared key then click on Continue and wait for the good to go message again.
If it is, then click on
Save Config and do this after
Apply for each setting you change.
Next bit > click on Advanced/Configuration/Advanced/Device Management and change the Expire to auto-logout to something more suitable as you'll end up being auto logged out before you get the rest of the settings in - I have mine set to 15mins > Apply > Save Config.
Next is Time Zone, for the UK it needs to be changed to (GMT) Dublin, Edinburgh, Lisbon, London and that is the next one above the default in the dropdown > Apply > Save Config.
Firewall/Intrusion Detection > Enable and tick the box for Log > Apply > Save Config (do i have to keep adding this bit on the end by now ?)
No doubt you will have updated the firmware on your Linksys at sometime and the procedure is probably similar, but you must be wired up and when you are invited to reboot, you
must change that from Current Settings to Factory Settings and the current f/w is 1.06g
Any downloads/news can be found at
http://www.billion.uk.com/esupport
Once you have that lot set up and have Save Config - then you can back up the Config and later restore with if need be (providing it's for the same f/w) and that's accessed via Advanced/Configuration System > Backup/Restore which you will probably have already noted.
The ADSL Mode can be viewed/changed via Advanced/Configuration/WAN/ADSL Mode
SRA Enabled should only be done if your ISP support it at the Exchange and PhyR is explained at
http://www.spaldwick.com/broadband/billion-7800n and this site also gives you basic settings for tweaking the SNRM and by experimentation - values of 5 in between.
This site will explain how to access the hidden page, but instead of adding /snr.cgi to the login URL - use
/snr.html as some have found the cgi a bit buggy.
I've found that PhyR has kept the SNRM artificially low, so I don't use it, but that will be your preference from your own experience when/if you enable it.
When you first go into the tweaking page, the value will probably be set at 0 but really should be -1 and that is what you use when you want to revert to your original profile.
Any changes you make to the SNRM are always from the original setting and are not cumulative and will effect a reboot.
Save Config on the main page to save the setting after it has resync'd.
Advanced/Status/ADSL Status just gives you the bare bones and the FECs and CRCs etc are viewed via Telnet.
Don't know which OS you're using and if you know that Telnet isn't auto enabled in Win 7.
This is enabled via Progs & Features/Turn Windows features on or off > scroll down to and tick the box for Telnet Client
To log into the router using Telnet > from Start > (and Run ?) type telnet 192.168.1.254 > Enter
You'll be presented with a cmd window and after it has connected, invited to log in.
This is the same as when you normally log into the router except, that you press Enter after the username and again after the password.
It doesn't tolerate typos and you can't backspace and you won't see the cursor move when you're entering the password.
At the next cmd prompt type
adsl info --stats > Enter and for the rest of the adsl cmds, it's
adsl --help and for the rest of the Telnet cmds - just type
help >Enter
At the top of the stats page, Trellis should be on by default but there was an instance where this wasn't the case and to switch it on, the cmd is :-
adsl configure --trellis on
Lower down the page in this article is an explanation of Trellis if you need it
http://www.kitz.co.uk/adsl/error_correction.htm
From that list of cmds, for subsequent help, the cmd is the same - type the category --help
The instructions for assigning a static IP for perhaps a printer, can be found on the esupport site as well as other How tos and I think that's about it.
I don't know if it would help if you copy & paste this lot into a Wordpad doc or something and then print it out....