It,s hard to say as different windows vary a bit, but are the beads internal or external? If they are internal then the rubber is usually part of the bead and a stiff flat knife under the bead should do the trick
hi sounds like wedge gasket .
start from the outside of the window and using a blunt wood chisel ease the black rubber gasket out ,once there are all out go inside and push the glass forward ,mark the beads in order they come out, top,bottom ,left ,
right. they should come out easy with a flat scraper, then remove the
glass (wear gloves) then when refiting the unit fit the glass,the beads,
then the rubber seal.