I'd look in FamilySearch, Catalog. That's where you'll find the non-indexed records. You can look for the will/probate in the digitized microfilm.
The Rutherford County Archives, www.rutherfordcountytn.gov/archives/index.htm
has probate records 1800s-early 1900s.
Since you know the details of what you want, you can contact the Rutherford County Clerk and ask if you can order a copy. Successful Searching!