I fitted an aftermarket SatNav unit a few months ago! I was looking at the Sony w\ Tomtom, but from what I understand Tomtom screwed up the integration and it didn't work, so Sony scrapped the model! Are you sure it's been tested & is working?
The AMI interface won't work, so your iPod will have to be connected to the new HU, make sure any unit you buy is compatible with it & you can obtain a lead. Bose will work fine, connect it to Amp outputs on your chosen HU. and your steering remote will require an adaptor ... Connects2 or Autoleads should have something compatible - google.