You can buy master sockets legitimately but they won't have the BT logo on and someone from BT may make a fuss about this in future (depending on how much of a jobsworth they are). Sometimes you may be able to find used ones with the BT logo on on sites like EBAY.
The type of socket you want is called a NTE5. It has two big screw terminals on the back for the network side wiring and then a section at the bottom with krone terminals for your extention wiring. If you are having trouble finding a local supplier you can order them from CPC, farnell, RS or clairity.
Messing with the wiring before the master socket is a bit like cutting service fuse seals, you aren't meant to do it but lots of people do so anyway and generally the worst BT tend to do is charge you for putting stuff right.
An incoming phone line is made up of two wires, it doesn't generally matter too much which way arround they go. If there are more than two wires then you will have to work out which pair are your phone line by trial and error. I would put the master socket where the cable enters the property to avoid having to join wiring on the BT side.
As for broadband there are a few ways to do it but they way I would reccomend if installing from scratch is to fit a filter plate (which replaces the bottom part of the NTE5) with both filtered and unfiltered terminals on the back (e.g.
http://www.clarity.it/xcart/product.php?productid=16134&cat=262&page=1 ) . From the filtered terminals you wire to your phone points as normal, from the unfiltered termins you wire to the middle pins of a RJ11 socket where you want to place your broadband modem/router.
As for tools you will need all the obvious tools for actually fitting something to the wall, a screwdriver and wire stripping tools to connect the incoming line to the big screw terminals and a krone punchdown tool to connect the extention wiring to the terminals on the bottom part. Krone punchdown tools come in a variety of qualities from cheap plastic ones that can basically be considered disposable to the genuine krone ones that those installing phone kit every day use. See
http://www.clarity.it/xcart/home.php?cat=257 for a selection of qualities.
