In my opinion, it's possible, but not as a person per say.
After my grandfather passed away, he would come to me in dreams and give me advice. He never gave me advice in life, but he did in my dreams and this lasted for a couple of years and his advice always steered me in the right direction.
It may be different for other people. Sometimes I think they might come to us in the form of strangers or even guardian angels--just my thinking because at times a stranger has seemed so very familiar to me.
I don't believe that guy on tv at all though--John Edwards, I think his name is. I have a very hard time believing his shows at all.
I have a suggestion. You can write a letter and say goodbye and say all the things you wanted to say and then seal the envelope and put it away in a box. Address it and everything. It sounds like you need "closure". The letter will help you gain the closure you need. We all need closure after we learn acceptance.
I'm very sorry to hear about your loss.
