Great, here is the code I used to get the move working. Right now it just moves some number of units. I plan on adding functionality for deciding how far to move it.
....
MSElementDescr* eledscr = 0;
UInt32 filePos = 0;
if (SUCCESS == mdlAssoc_getElementDescr(&eledscr, &filePos, eleId, attachment, FALSE))
{
//rc = (SUCCESS == mdlElmdscr_deleteByModelRef(eledscr, filePos, attachment, FALSE));
Dpoint3d pntP;
pntP.x = 100000;
pntP.y = 100000;
pntP.z = 0;
Transform tMatrix;
mdlTMatrix_getIdentity(&tMatrix);
mdlTMatrix_setTranslation(&tMatrix, &pntP);
mdlElmdscr_transformAllowModification(&eledscr, &tMatrix,attachment,attachment,0);
mdlElmdscr_rewrite(eledscr, eledscr, filePos);
mdlElmdscr_freeAll(&eledscr);
}