My 6 yr old son has hirshsprung's and temporary ostomy. to verify, the last procedure would be pull-thru after transition zone and closure of ostomy.

Correct: Correct; it is common to perform multi stage procedures for hirschprungs. The results are usually good and allow the child to live near-normally although a bowel regimen to avoid constipation is usually required.

Yes,... usually: You should verify this with your son's surgeon. But typically the affected rectum is removed and then normal rectum is reattached. The surgeon may need to perform additional biopsies first before this surgery to identify where normal rectum ends and the affected rectum begins.