I've just done this and had a whole heap of trouble with the back seat... The seat I removed was a 40/60 folding seat, the one I put in was a one piece. I had to make up brackets for mounting the rear seat and also for the the armrest. The side bolsters are part of the seat with the one piece but are bolted to the car on the split seat so it was a bit of a pain to get them to sit right. Was hard work but well worth it in the end.
I just unplugged my airbags and re plugged the new ones in, nipped down the main dealer and got my mate to put the airbag light out. If you need any advice on getting the front seats out give me a shout - its sooo easy!