You should retain an attorney. You cannot file a lien without a judgment. You will need to file a lawsuit to get a judgment. For this amount of money, a lawyer should be used. You should be able to find someone to handle it on a contingency basis.
Although you cannot obtain a lien without a judgment, you may be able to obtian a prejudgment "writ of attachment." This remedy does require you to hire an attorney. A writ of attachment works much like a lien. It is available only in certain contract actions where the amount in dispute is reasonably calculable and the plaintiff can demonstrate likely success. Lawsuits often quickly settle when a plaintiff obtains a writ of attachment. Your matter appears to be the type of action that would permit a prejudgment writ of attachment.