I have attached photos that the Warren Historical & Genealogical Society have of the WILLIS & BERGER headstones. The Berger marker is in row 2 and the Willis ones are located in row 23 (from the west end of the cmemtery). This is the end that was once owned by the Methodist Church. If you would like a copy of the cemetery listing please call the Warren Historical Gallery Office at 586-258-2056 someone will return your call. I don't remember the cost, I do know it was less than $5.00.
If you are interested in a photo of the marker showing Henry Willis, I can try to take it when the snow and mud clear up a bit, it looks like it is up against the back fence.
Hope this helps.

Becky Hetchler
Warren Historical & Genealogical Society
whgs.glis.net
warrenhist@yahoo.com