@orienteer I would feel the same if I were you! Here are some things that might be a consideration on your decision -

I’d want more detail about why they recommend a lumpectomy for a small DCIS 0, grade 1, ER+ lesion? These days active surveillance is often suggested, maybe starting hormone therapy to see if it regresses. I believe AIs can reduce lesion size in ER+, perhaps making it possible to leave the nipple in place?
If you are pre-menopause, though, that does involve more issues. Or, there may be other reasons that they suspect this lesion requires surgery now.

Have you had an MRI? I’d probably want one before making that decision.

You might want a second opinion from a highly rated comprehensive cancer center. In fact, you really might want to do this if you think you might continue to question whether you made the right decision. Second opinions are not unusual. They involve paperwork, sharing health history (from electronic health record), sending scans and biopsy if available (most can be done by facility sharing once you give approval, you don’t need to actually mail anything). Insurance usually covers 1-2 second opinions, but out of pocket isn’t terribly high. Since most lesions can’t be felt, they probably won’t need you to have a physical visit. You might want to ask for a video visit, though, so you can hear the results from the physician.

In 2022 when I was diagnosed with a similar DCIS, the recommendation was for lumpectomy, radiation, hormone therapy. The cancer center where I go has changed their guidelines and they now more often suggest active surveillance. In my case, I might have still wanted the surgery, as the local radiologist reading my diagnostic mammogram miss-labeled the lesion as an unusual lymph node. A MRI caught what the mammogram missed for the type lesion my body grows - but I’d be concerned that it would be missed again if the only surveillance I could get would be mammograms.