Put the rear casette back on the freehub and use this to pull the whole assembly off by putting both hands/fingers around the back of it,theres more leverage by doing this and it will usually come off easily.
It works best if you hold the sprockets against the pawls slightly as you work it off,remember its best to use alloy freehubs with alloy cassettes,steel/steel,as steel cassettes causes wear on the alloy splines,causing it to jam. 😥
Be carefull not to loose small parts,and remember to fit the washer between the wheel bearing and freehub body,I would replace the plastic free hub to hub seal as well,I would avoid using grease to lube,automotive oil works best or a light three in one oil.
getting everything clean is vitally important,I use brake cleaner as this evaporates quickly, and leaves no residue unlike a dry lube.
Try to press fit new bearings using a peice of threaded bar/nuts/washers and the old bearings,avoid steel punches and hammering on replacment as it can cause damage imho. hth 😉