I am sorry I misunderstood your abbreviation. I thought SIL was siblings. That being said, yes, genetic testing on the tumor will help guide treatment.
There are many pages with DCIS members, but no one will have exactly your cancer, even though they might have the same treatment plan. If you go to the breast cancer page of discussions and type DCIS into the search bar it should bring up a ton of discussions.
I feel like the nurse, if she is at the surgeons office is kind of jumping the gun by giving you treatment options. If your surgeon doesn’t refer you to an oncologist, I believe you could ask for that referral. In my humble opinion only a cancer doctor should create cancer treatment plans. I personally have had surgical oncologists, and radiation oncologists, and medical oncologists, in my case I found that I preferred it when my medical oncologist led the team.
I would ask every question you have and if some of those get deferred to medical oncology, that just gives you more chances for even more questions.
You got this, please let me know how that goes.

Genetic testing is for genes that we pass along (or inherited ). Genomic testing is when they test your specific cancer and it is from tissue from your tumor. The pathologist that did your original testing at hospital sends it for genomic testing. Genomic testing does need to be ordered by one of your MDs.