Ello
Right... answering your questions first:
What else do you need? You will need wraps (at least 4), and liners, and somewhere to keep the dirties (a lidded bucket). A mesh bag is handy so you don't have to handle dirty nappies... I am useless - never got round to getting them so I handle and wash hands obsessively!
Where is best to get them? Well... I am biased and have to say BumFluff as that is me , but kittykins, thenatural baby resource and twinkle on the web are great - I can sell anything that babykind lists
Liners? It all depends on how much you want to deal with poo. Disposable liners means you just lift it out and flush down the toilet as one, fleece/silk mean rinsing (solid poo falls off, breastfed poo just shoots through so comes off in the wash... its teething/early weaning poo that can be messy) but save you money in the long run.
Poo? Yup, just chuck it down the loo
Absorbancy? They are all different - most need extra boosters for night. A bamboo nappy will easily go 4-5 hours (mine can go 5-6) during the day, and a nappy with boosters will cope with a full night.
Changing - normally after about 4 hours. Not after every wee.
How many? I tend to say 16 - that usually allows you to wash every 3 days and have time for them to dry naturally.
If you want to ask any more questions or want some more specific guidance on what to choose then feel free to email me bumfluffnappies at gmail dot com - I am disturbingly besotted by nappies and enjoy the chance to ramble on at a potentially interested person