If you're adamant on doing this yoursekf, first look at a cheap network tester on ebay, while you won't get any great info out of it, you'll be able to spot any crossed over cables, then you'll want an IDC Professional Cronin tool, I'd recommend buying a few of these as if they break half way through a job you'll get horribly frustrated, cable strimmer. a few boxes of 305m CAT5, and of course patch panels, patress boxes face plates and trunking if required.
If you've got an accessible false floor running the cables isn't usually *too* bad, if not, you'll need a decent drill, with spare batteries, and a lot of drill bits, I'd also recommend in a cable fish kit.
By this point you're ready to go except you've probably just spent the same amount in parts / tools as it would have cost to have someone come in and do it, this is useful if you plan on doing more than one install. Terminating the cables isn't difficult just match them up with the colours on the back of the patch panel / network sockets (there will be two sets of colours for A nd B standards, make sure you use the same on both sides, and KEEP THIS UNIFORM!!). After this you'll just need some patch leads to go from your patch panel to your devices (Computer, Switch, etc)
Hope this helps, or at least puts things into perspective as to how big a job this quickly becomes.