I did exactly the same as SWMBO suffers with a bad back and the twin seat caused her to lean into the middle slightly.
My van is a startline so no extra air bags in the seat itself (or heating elements) so just 8 nuts to undo and 4 fixings to remove from the floor. 2 holes in the flooring are hidden and 2 end up on show by the handbrake. You can get ‘bungs’ from ebay for about 12 quid to hide them.
I got a matching seat from Exploria and have since added arm rests. The seat was from a van so is missing a bit of trim low level at the back. I’ve not done anything with the airbag as only a problem if going from a single to a double.
Genuine OEM seat covers can be purchased from Inka Corp on ebay or you may get them from convertors as people go for leather.
SWMBO says its so much more comfortable than the double. I only got £120 for the old double seat but hey ho!
Ian