I’d clean off both the frame and the top , then buy a good D shape seal from 3M that is adhesive backed on one side. Might upgrade to a little thicker wider one. They also have a B shape that may seal better , I don’t Remember just how wide the sealing surfaces are on the tops , been several...
It’s a bit hard to tell for sure but isn’t this a clip pin that holds the front stabilizer mount, if so just pull this pin and slide the bar off the front mount to allow the arms to move out farther to hook up.
I would be buying sealed if it were mine. Here are pics of each type. The first is the friction bearing that has a solid spool that slides on the axle and two clam shell halves that bolt around it, the only lib it gets is any grease that you apply each time you use it.
The second is the...
The inner filter is basically a safety filter in case something gets past the outer primary one. The NX comes with the primary filter only and no inner safety filter. The inner filter pushes into the plastic housing first then the primary goes over the inner filter and seals into the housing.