Wear of mating tooth surfaces modifies the tooth profile and the local contact state, which in turn changes gear-mesh excitation and system vibration. This paper examines how rough-surface contact and progressive wear jointly affect the response of a gear pair. A multi-stage fractal contact formulation accounts for the deformation of asperities at different scales and supplies the real area of contact. Contact pressure calculated from that area is used in an Archard-based wear calculation. The resulting wear states are incorporated into a six-degree-of-freedom (6-DOF) model with coupled translational and torsional motion, time-varying mesh stiffness (TVMS), static transmission error, and tooth friction. Simulations at four wear stages are compared in terms of profile wear, meshing force, and vibration. Wear is concentrated near the beginning of engagement and is much smaller around the pitch point, although its overall spatial pattern changes little as the number of cycles grows. Progressive wear raises both the maximum meshing force and the range of its fluctuations; it also increases pinion acceleration and spectral components associated with the mesh frequency. Relative to H1, the maximum force at H4 is 20.63% higher, and its peak-to-peak range is approximately 9.15 times that at H1. The analysis connects stage-dependent rough-surface contact with the evolution of gear wear and its dynamic manifestations.