U.S. States: Texas: Grayson County
Most of Grayson Co, TX cemeteries are online, under the archived segment of the GenWeb Project.
Try the public library in Sherman, they have a nice genealogy collection, they should be used to genealogy research questions regarding obituaries. If they do not have the old back issues of the newspaper, find out the name of the local newspapers for 1878 time period. Contact the University of TX at Austin, they have the largest collection of TX newspapers. They will not do research, but if you have date and name of newspaper, they will do "lookup" for an obituary. If they find one, there will be a nominal charge for copying and postage.