It can be done just with a lot of fiddling to get the screen in from the airbox hose but as on this occasion it doesn't last, I suspect the previous owner had done just that.
To do it properly you need to remove the airbox hose, battery, battery tray, petrol tank, seat , side panels , rear inner mudguard and the electrics so that you can free the airbox enough to do the job properly.
I've never worked on a Himalayan , what's involved in removing the battery ?