Probably a good time for my first post on the forum here, so hello to all :)
To confirm the MAC Address on the LX800 does start differently to the conventional 00:1A:79, it'll be something like 78:02:B2.... The MAC in the Portal Settings should match the MAC on the sticker on the underside of the box, you can use either one to pass to the provider providing they match, but if they do not match for any reason or if in doubt then always go with the MAC in Portal Settings, this is definitely the one the hardware will be using.
If you go to MYTV > Portal Settings > Portal 1 and scroll right to Server URL > OK then you can enter your providers URL here, needs to be in full format for example
http://your.providers.url.com:25461/c <- This will of course be specific to your provider so get the info from them on what this needs to be, it is the same one they will use for MAG/Stalker type boxes.