Sky+ to sky Hd upgrade

[kejhj]

I have a sky+ box (white one, non hd) and looking to change it to a sky hd box.
What is the best way to do it? Am only on the family package, so not really interested in films/sports.
Do I contact sky? or buy 2nd hand box and do it myself, obviously I will have to pair the card to the new box so sky will know anyway.

Any advice