Where can I find help on signing over my parental rights to my son when I haven't had much contact with him in the past 5 years due to being military

Through the court system. Look it up on your gov's web site

First, have you read the many other threads here about that? Second, what do you expect to gain by doing so? Third, does your ex's new spouse want to adopt him?

Bottomline is a court has to grant a relinquishment of rights. They are generally granted ONLY to clear the way for adoption or if the parent represents a danger to the child. They are NEVER granted just to allow the parent to get out of child support. Even in the unlikely case it is granted, only the rights are gone, not the responsibilities.

So maybe you need to re-examine your motives here.