There is a lot of information regarding vit-D and MS (as well as a heap of other good inforamtion relating to the treatment of MS) on the following web site
www.overcomingmultiplesclerosis.org
The professor who run this web site (Prof. George Jelinek) was diagnosed with MS 11 years ago and has done considerable research into lifestyle changes to help with the treatment of the disease. He has since remained symptom free.