Depressurise the system before you pull any airlines, even on access and jacked up you'll get a nasty surprise.
If you can depressurise then get a very sharp knife and with care, carefully cut into the bag for removal. The moment it start to hiss, let it deflate by itself.
sometimes the rear airbag tops can be seized into place with rust and road dirt. A bit of a levering will shift them and then wire brush the airbag top seats as best as you can ready for the new dunlops. I got all four from island4x4, eurospares were the company who supplied mine.