[DaveNP]

I've not done it recently but I've changed covers and swapped foam on a number of cars and once you get going it isn't as hard as you might fear. You'll need to get to the underside of the seat so you have to take it out, generally disconnect any electrical plugs then unbolt the seat runners, pushing the seat back and forwards as needed. I used a good pair of side cutters to cut the metal hog rings, opening them up was not going to be easy so cutting was a better option. Work methiodically and carefully and don't rip away at anything, there is probably another connection that needs undoing if it doesn't come off reasonably easily. As Kiwi says zip ties are the way for putting it back together, they're quite strong and easy to use.
You end up turning the seat upside down and round and round as you do it so somewhere clean with a bit of space will save frustration too.