Tamoxifen vs. Arimidex

Hi;  Thank you for taking the time to review my question.  A quick background:
1. I started chemo treatment (ACT) in June 2008, and at that time I stopped having my periods.  
2. After chemo ended in Nov. 2008, I was put on Arimidex because my blood tests showed that I was POST-menopause.  
3. However, just a few days ago, surprisingly I started having my periods again (9 months after finishing chemo!).  
4. My Surgical Pathology Report shows "Estrogen: Positive > 75% tumor ___ staining"

So, now that I'm back to being PRE-menopausal, I assume that my oncologist is going to recommend Tamoxifen. So, my questions are:
Q1. What are the risks of going from Arimidex to Tamoxifen?
Q2. What is the best way for me to discuss with him about the benefits vs. risks of taking Tamoxifen?
Q3. Should I wait a while (how long?) before I start taking Tamoxifen?

Thanks! -Krista

[japdip]

Duplicate post / answered below.