Important not to be too rigid with plans - just do as much hilly running as you can with over excercising. I once over did it on on my BG training (two long days back to back) and had a bad ankle for 3 weeks afterwards. I would say do one run/walk with as much ascent/descent as possible each week. and then whatever else you feel comfortable with. I found long bike rides really helped as it develops the climbing fitness with no load fatigue, and swimming is great for easing of the muscles.