Upper GI series showed internal hernia in small bowel, but CT scan did not, will I need surgery? What is hernia surgery like?

Simple. you have to had a previous surgery to have an internal hernia and the need for the surgery depend on the symptoms and the surgery usually simple could be sometime done laproscopically depend on the nature of previous surgery and expected adhesion i hope that answer your question good luck.
Lap hernia repair. CT scan does not always show an internal hernia. If you're having symptoms, then you probably need surgery. It can be done laparoscopically, through small incisions. It involves returning the bowel to its normal position and closing the hole on the inside through which the bowel migrated. Lap internal hernia repair typically is well tolerated. Internal hernias after a B2 are not uncommon.