Hi all, for a wile my passenger side seat has had a little rock (movement) to it yesterday i desire to look in to it after i went for a trip to Ikea for these

best things to come out of Sweden ever [Y] and wile i was turning i could here the chair rocking so though would see whats the problem.
Any how!, i found that one of the wheels that sit in the runners had died a death so my Q is is there a giude to remving the wheel and replacing it, also a part number if possible for a new wheel if VW supple the wheel separably. If not i have a spare set of seats in storage i can take the wheel off so mainly looking for a guide to replace the damage wheel.
what it should look like [wheel nearest to the door]
the damaged wheel [nearest to handbrake]
as you can see the wheels destroyed
Thanks in advance
Mike