You can call your Management and maybe workout a better payment schedule then 500. Maybe 250 and 18 months or something to that affect, etc.
Also get involved with your board and go to meetings, and learn why there doing such assesments, maybe its something they neglegted for years.
Your concerns are real. We highly recommend becoming involved. The HOA meetings are open to the public and owners are provided the opportunity to express themselves.
It is time for you to take advantage of this right and make your feelings public. We suspect you will not be alone in your cause.