I did both on my 4.0. Really easy. Just unbolt the covers, clean up, silicone the corners, put new gasket on, bolt cover back on.
(may be necessary to move some other things out of the way first - had remove upper radiator hose on mine, but I think that was it)
Jayboy -Sent from my iPhone using FRF App
1999 4.0L supercab. 4dr, 4x4, 5spd - All stock except some accessories and small upgrades to worn items.