Hi skrobe, I don't know about your Branson but on my TYM 273 the sight glass is encased in rubber and just pops out (use a narrow flat screwdriver to work it out). Park the front end in a depression so the rear is raised up some and Hyd oil flows toward the front of tractor, then pop it out, clean real well, use a dab of silicone, let dry several hours and you should have leak stopped.
Good luck, Greg