There is an index to some Morgan Co. probates on the MAGA website: http://www.rootsweb.ancestry.com/~ilmaga/index2.html
There are also online at FamilySearch.org under Illinois Probates. The images are browse-able so you can choose Morgan and then the correct index book. In addition, the LDS microfilmed records can be ordered through FamilySearch. Last but not least, you can find out if there is a probate or will for him from the Circuit Clerk's office or the Jacksonville Genealogy Society. Good luck!