You just need to remove the rubber seal tubing around the door frame, take out the rear cushion by removing the single bolt holding it on then just pull on the door card until it unclips.
I was using Dunlop Wintersport 3D last year when it was snowing. My house is half way up a quite steep hill and it managed to climb it without any issues whatsoever.
Haven't actually used them at all this year though as it's been too warm
I got most my mod's from Nathan @ Japex also. Really easy to deal with and you can usually negotiate a better deal if you speak to him directly over Skype.