Trying to get some lineage on my old unit from the 90's. Anyone have any knowledge on the 115th FSC , 1st CAV out of Ft. Hood?

You can always look up the unit on AKO and research the Department of Heraldry site that lists the unit/campaign/year. I found proof of a VUA from 2003 almost 10 years later. From there, just print out the page and hit PAC with orders proving you were with the unit at the time. If you are really lucky, the UIC is already listed on your ERB.