Ok, nevermind... I got something working about 3 minutes after posting this question. I'll paste below what worked for my needs. Maybe this will help someone else, or maybe you all have a more direct method to achieve this.
def main(): #inputs to the Xpresso Node are Link (named "LayerLink") and Float (named "FieldtInfluence") myObject = LayerLink myTag = myObject.GetTag(1019364) myTag.SetParameter(c4d.ID_CA_CONSTRAINT_TAG_AIM_TWEIGHT, FieldInfluence, c4d.DESCFLAGS_SET_0)