We've spent quite a bit of time there - Apgar & St. Mary will have sites for you - stay away from Two Medicine & Many Glacier (for campsites). That being said, our favorite area in the park is Many Glacier. We've posted a lot about Glacier on our blog -
www.RVingandtravels.com. Use the Index on the right and click on Glacier. Feel free to PM if have specific questions. You'll love the area - one of our favorites!