Want to add my own cable to my Sky dish LNB

[FeFiDoh]

We have a quad LNB on our dish with sky+ HD downstairs and sky+ upstairs. It use to be normal sky box upstairs until I got this box from a friend so it only has the one dish input, how hard is it to add a new cable to the LNB?
I did have a quick gander and it just appears to screw in and then you run it to the new box, any precautions I need to take?

Dont really want to pay sky just to come and fit 1 poxy cable and have them charge me about £50 for it

 

[FeFiDoh]

Well hole s already in the wall so hopefully its big enough for another cable

kefkef thats damn cheap was looking on ******s and they charge £22 for 20m! Ill order it now I think so I can get the Sky+ working properly

 

[FeFiDoh]

Already got the card paired to the box just lacking the extra dish input so I can record one thing and turn over

Cheaper than getting sky to do it! Shouldnt take long to do either, stuff got sent out today so hopefully here for tomorrow woop