Federal Restitution is something that is under the direct oversight of the Federal Probation Service. If you have been released, and are seeking to satisfy your restitution requirement, it is very important that you review your request with your probation officer. Be careful of any orders that you make no contact with the victim directly, as making contact could be a violation of your terms of release.
While on probation, the best course of action is to go through your probation officer, or through your own attorney.
I agree with the first answer given. However, if I understand your question, you really want to know whether your attorney can negotiate the amount of restitution ordered by the court. The answer to that is "Yes" he/she can do that, but it should also be brought before the Probation Department almost simultaneously so that nobody in the Probation Department gets the notion that you've been trying to go around the Court's order of restitution.