Use the part number off your turbo and buy the right kit, it'll come with everything you need. If the compressor or turbine are damaged though they need to be bought separately.
The nut on the compressor end is a left hand thread too and remember you'll either need to mark the nut, compressor wheel and shaft really well so you can put it all back exactly as is or it'll need to get balanced.
That nut comes off then the compressor wheel then the turbine wheel and shaft come out then you split the cartridge. Lay all the parts out one at a time as you dismantle it in the order they come out so you know where it all goes back in.
For the housings the cold side is just 6 little bolts and off it comes but the exhaust end will probably need a good soaking, those little 10mm bolts can break quite easy and the housing is often stuck on quite well with the heat, rust and carbon. It'll need a bit of hammering to get it off. Just look up vnt cleaning for more on that.