If a warrant has been issued you have to go to the court that issued the warrant and ask to be placed on calendar to have the warrant recalled. It usually takes some time to get a court date, though, so don't delay.
When in court, you can address the issue of the fine with the judge. If there has been some error (it happens more often than you might think), the judge can address it. If the amount is not for restitution and really is for a fine/assessments/fees, the court may be able to help you with more favorable payment arrangements or modifying the amount, converting some to community service or the like.
If you wait you could be arrested on the warrant, or ordered to appear in court at an inconvenient time. It is always better to take these matters directly to the judge yourself than wait and have the warrant process take you to the judge. I would recommend that you consult an attorney in your area who can help you with this issue. He or she may be able to resolve this for you much quicker than you can by yourself, and be able to advise you as to the options you may have in your jurisdiction.
Normally on a failure to appear if you put yourself back on calendar and then go to court with your excuses you will not be taken into custody. If you are stopped for a traffic violation and the warrant is discovered you will be arrested and taken to jail. An FTA is usually punished as a contempt unless you take care of it voluntarily. A typical sentence in SF where I practice is 5 days in jail.
You can avoid that by taking the initiative and putting your case on calendar. It would be most helpful if you found an attorney to go to court with you. Both courses of action minimize the chances of an arrest.