Does anyone based in/near Vicksburg know if the Military Park is staffed at all at present? The rangers there have such extensive histories of those who fought there. @EGamer, perhaps you could call the park at 601-636-0583 to inquire about Mr. Eckes. Even if the Visitor Center is not open to the public it may be that some of the historians or employees there can offer you any assistance.
Also thinking that if it's stories you are looking for, the licensed battlefield guides at the VNMP, which might be reachable by phone or email, generally know a bunch of the interesting personal stories and details of the men who fought and served there.
I recently finished reading Tim Smith's book "The Union Assaults at Vicksburg" and he has an extensive bibliography. I will toss out a few that I see and page number listed in bibliography.
Letters & Journals at Vicksburg NPS.
John O'Dea, " A forlorn Hope" -- pg 453 . . . Original in Chicago Times Herald, May 30, 1897 and reprinted in John O'Dea, "A Forlonrn Hope", in Transactions of the McLean County Historical Society, Vol 1 (Bloomington IL: McLean County Historical Society, 1899), 477-480.
J. B. Allen Letter, 30th Ohio File -- 452
Robert McRory Letter, 30th Ohio-- pg 453
W. Schalenburg Letter, 37 Ohio File -- pg 453
Thomas J. Taylor Letter, 47th Ohio File -- pg 454
More references from Footnotes:
September 29, 1910, National Tribune.
Brinkerhoff, History of the Thirtieth Regiment Ohio Volunteer Infantry, 72-73, VNPS
History of the 37th Regiment, O.V.V.I., 21-22
J. B. Allen to W. T. Rigby, July 12, 1904. 30th Ohio File-- VNPS
Robert McRory to J. B. Allen, APril 15, 1904, 30th Ohio File-- VNPS
Isaac T. WIlliams to brother June 18, 1863, Isaac T. Williams Papers, Tim Brookes Collection USAHEC.
W. Schalenburg to W. T. Rigby, March 12, 1901, 37th Ohio File-- VNPS
Henry Schmidt to wife, May 24, 1863, Schmidt Family Papers, Filson Historical Society, Louisville, Kentucky.
Saunier, A History of the Forty-seventh Regiment Ohio Veteran Volunteer Infantry, 147-148
Clarke, Reminiscence and Anecdotes (accounts of a member of 36 Mississippi Regiment)
That is just a few that I could match up with first hand accounts of regiments in the Forlorn Hope. There are probably other accounts from the Confederate side. I recommend you borrow or buy Tim Smith's book.