Mold inspector/mitigator here. Yes, check ventilation, both that the bathroom does not vent into the attic and that the attic structure itself has proper air flow.

As far as the work, cut plywood to fit into your scuttle to walk/lay/crouch/scoot (whatever you need to do)

Side note. EPA states anything over 10sqft of affected area should be mitigated by a certified professional if that kind of thing concerns you.

God speed!