Do you think these three years spent abroad will be an obstacle/problem obtaining Citizenship?

With only a few exceptions, when a Permanent Resident ("Green Card" holder) remains outside of the U.S. for a period of three years, that person is deemed to have abandoned his/her residence in the U.S. and his/her status as a Permanent Resident. In the naturalization application process, an applicant must identify all trips he/she has made outside the U.S. during only the immediately preceding five years. If after a 3-year absence a Permanent Resident is admitted entry back into the country as a Permanent Resident, and 17 years later applies to become a naturalized citizen, the applicant may expect to succeed in naturalizing. A single speeding ticket ten years before applying for naturalization will not stand in the way of eligibility. It would be wise to consult with an immigration attorney about all details relating to naturalization eligibility.

I think it was too long ago so you should have no issues. However, it is best if you consult with an Immigration attorney in your area.