Welcome to you, you will find everything you want to know about your Z on here. As to buying parts all the usual parts suppliers will have most stuff and BMW will have everything but usally at a price. It is always worthwhile getting a price for a particular part from BMW as in some cases they will be cheaper than the other suppliers, I use Sophers BMW in Peterborough who give us Forum members a discount when you mention the Forum when ordering with them on the phone. Have also blagged a discount with my local BMW dealer, Synters at Newport and Cardiff. Loads on ebay new and used parts, I also use Carparts4less online, they are the Web only side of Europarts and always cheaper than Europarts but worth checking on both sites and always use their current offer discount that is on their home page. For oils for engine gearbox and diff lot of us use Opie Oils online shop.
Equip yourself with a code reader that will read engine and airbag faults and clear them, threads on here with suggestions what code reader to get, you will need one eventually!!