Judgments are very difficult to "remove," but you may ask the court by motion to vacate the judgment based on any deficiency of service. Maryland allows alternate service in certain circumstances so before raising an objection to the service one should fully understand the rules surrounding service of process.
Note that Maryland law imposes strict timelines for filing motions and so forth. It may help to have an attorney review the facts surrounding service as well as the critical dates in your particular case.
