Hi there...I just read your post on the roll call, what an interesting background! I am in Detroit, your neighbor to the South! I did not realize you were in Canada...
As for the family history, they say less than 10% of breast cancers are hereditory, and they say that BC under age 40 can be a sign. Have you checked out FORCE? There is a wealth of information there, about risk for inherited cancers from the BRCA mutation. It sounds like it could be a good idea for you to seek genetic counseling to evaluate your risk and possibly test, so you know how to fight best.
To answer some of your questions...
Herceptin has nothing to do with ER/PR status. SOme cancers overproduce a protein (?) called her 2 neu. An overexpression means that the cancer may respond to a drug called herceptin. Recently it was approved for use to prevent recurrance in early cancers, when I did chemo (2000) it was mainly used for stage IV. It is not considered a hormonal drug like Tamoxifen, they are unrelated.
A MUGA test is easy...it is measuring something with your heart, to make sure it can tolerate the chemo. The test is painless and you may even fall asleep on the table.
Knowledge is power! Consider taking a tape recorder too, when you see the doctors, it is impossible to get it all at once.
And keep asking those questions!