hya pal, with a double-din unit it all depends which one you get will depend on how much of the stuff you listed you will need. If you have a bose unit, one thing you will need is a pac oem loom, which seem to be only available from the states. This will stop you having to cut into wires that lead to the bose amp and speakers. As for the rest of it, you may not need a harness, if you want it to talk to the steering wheel then there are plenty of items on ebay that are selling gadgets for this pretty cheap. As for fitting, its pretty straight forward once you obtained a pac oem adapter, I got mine from american ebay site but you could give bigphil a shout as he may be able to source em
If you want guidance pm H5 or Andy with any questions as they are pretty clued up with ice install
note to self, I really must get new shot of this, ive way over used this one lol