I think it's two plastic clips then. Have you done a search on the forum for any advice on this though? You may find some answers in the Gurus section. Failing that I'm sure when the sun goes in then more people will be on here to give more info..
You need to squeeze your nails into the crack on the lower side of the cover. Pulling gently upwards untill release. You should be able to see the tabs you must release on the new covers.
Fitting is the reverse procedure.
It's a good idea to have something soft on the ground in case you drop it.