A previously discussed potential energy surface for the CO molecule interacting with one Ar atom is extended to evaluate its dependence on molecular vibrations. The \v=0] and the \v=1] adiabatic potential energy surfaces are employed within a stochastic treatment to obtain the vibrational transition energy changes as the number of rare gas atoms around the CO molecule is increased. The present calculations yield shifts of the excitation energy for the (v=0-->v=1) transition in Ar cluster of variable size which are in fair agreement with experimental expectations for the limiting case of solid argon. The details of the preferential structuring and clustering of the adatoms around the dopant molecule are obtained from diffusion Monte Carlo calculations and are extensively analyzed. The specifics of the system behavior are discussed and a driving microscopic mechanism is suggested on the basis of the energy balance between the interaction potentials that are present in the title system.