Can you contact an INS agent by email for answers to questions regarding travel on a temporary green card?

I entered the US on a permanment GREEN card in 1963 married had two children born in the usa How ever in the early 1980's I had to return to Ireland to take care of my elderly parants. In the inter-viening years I have returned to The USA on a regular basis at least once a year How ever I have never held a job I would now like to become an United States Citizen. My permanment Visa card is still valid As I have not lived in US on a pernment basis for the last 5 years only visiting once or twice a year . Would appreciate your advice as to how I go about applying and what Form I should use Many thanks Imilda Keane