I would call and ask if you can wait until Monday to do the necropsy. Most times they want the body as soon as possible. You can try to do a home necropsy and take pictures of the organs for anything suspicious. The following link has pictures of Mareks findings in necropsies, and click on both “clinical signs” and “gross lesions:”
http://partnersah.vet.cornell.edu/avian-atlas/#/disease/Marek's_Disease
http://partnersah.vet.cornell.edu/avian-atlas/#/disease/Marek's_Disease