I've been having trouble sleeping for a while now. Does the Satcharita mention if Udi can help with insomnia?

Yes, a footnote in Chapter 33, attributed to R. Hari Sitaram Dixit, provides two specific examples of Udi helping with sleep issues. In one case, a friend of Dixit's had been unable to sleep for eight days and found no relief from a doctor's medicine. After taking Maharaj's Udi for just one night, he reported sleeping very well. Similarly, the chapter mentions a child from Bandra who had not been able to sleep for two months. After his father took him to Shirdi for Maharaj's Darshan, the child got sleep that very night and continued to sleep well from then on.