You'll need basic tools, a kettle, some teabags and at least one packet of premium biscuits. I'd go with Boasters.
If you're doing it on the drive you'll need some axle stands and the easiest way to remove the OEM exhaust is to chop it in front of the rear axle so you can take the rear section off once you've removed the Diffuser and then you can just unbolt the front section from the Manifold... NOW, if you've got a Decat then just refit everything as you'd imagine it to go on, an exhaust really will only go on one way. But, if you're wanting to keep the OEM Cat then I think (not certain as my two exhuast changes have been without the OEM Cat) you may have to cut the original centre section after the Cat and then join your new Cat-Back to this and refit as you'd expect.
There's not much to it really. The fiddliest bit is getting the Diffuser off without losing or breaking any clips/screws.
Check it's not blowing after fitting, the V-Band on the Manifold has to be REALLY tight to stop it blowing.