I just took apart the seats in Bill's Syncro to add heated seating elements.
So here are some pictures that should help.
If you look at the bottom of the seat there are 4 tore screws in the seat rail. These hold the lower seat cushion to the seat frame. I'm glad we decided to add heated seats to this van. All 8 (both seats) of these seat rail screws were less than finger tight. One wasn't in its hole all all.
In this picture you can see that I've already removed the front two. Just move the slide rail handle and the rails will slide back and forth (or just slide them off) to access the bolts.
The seat fabric is just held on by a 1/2' cardboard strip that is part of the upholstery. It simply tucks into a slot on the steel seat pan. You can just pull up on this cardboard strip to get it out of its slot or use a flat blade screw driver to help get it out. Helps to lean on the cushion to compress it a bit to give the upholstery some slack.
Close up of what the slot looks like.
Once you have pulled the cardboard retainer loose all the way around the seat cushion with fabric can be removed from the pan. So if you were just trying to swap in the fabric and cushion from the rear jump seat this is all you need.
If you want to swap the fabric to a different cushion then you need to free a few metal hooks that secure the fabric to the cushion. I don't have those pictures since in this case I just needed to access the underside of the fabric to insert seat heaters.
This is what went in these seats FWIW. Heating elements for both the upper and lower portion of the seat.
To access the upper cushion you simply have to unhook this plastic strip at the bottom of the upper cushion.
Hope that helps some.