Hi Adrienne. ..welcome to the site. The beginning is scary and so much info to take in.
I too have a her2 cancer (mine is also estrogen +) and was a grade 3, just ubder 2 cm. I had surgery 1st...I chose a mastectomy. ..and had a sentinal node biopsy. They inject a radioctive dye near the tumour area and track the nodes nearest this...this is how they choose which to remove. I only had 3 removed...but they might take less or more depending on how close they are. If any positive then they remove more in a different surgery.
The chemo part of my treatment is 6 months. The Herceptin. ..which they give you to prevent further her2 cell changes is for 12 months, starts about halfway through your chemo treatment.
I am sure you will have many more questions. I hope you have ordered the "My journey kit" through this site. It is very helpful...as are many of the readings available here.
Hope all goes well. Kath x