Consulting primary sources is a great way to connect with the music as it was originally written, and a must for serious research
The Grove article "Sources, MS" is a very detailed listing of manuscript sources, their contents, and facsimile and modern edition information.
Our collection has many facsimiles, including microfilm, black and white photocopies, full color reproduction, and collector replicas. Many of these are found in the non-circulating M2-M3 collection, and some are held in Special Collections due to their value. They are available for you to consult, and I encourage you to do so.
When searching for manuscript editions, keep in mind that they often have numerous names. The manuscript most know as Wolfenbüttel 1 (W1) is also known by its library shelfmark: Herzog August Bibliothek. Manuscript. Helmstedt 628 and also by a catalog number Manuscript 677. Try varying your search terms to locate a copy, and always research the variant names.
There is a wonderful database under construction, the Digital Image Archive of Medieval Music (DIAMM): http://www.diamm.ac.uk/ It contains links to digitized manuscripts as well as a vast amount of information about the source.