A harmonic analysis would be an efficient way to do it. You can add acceleration and apply it to a boundary condition. If you want to use mode combination, you can run a modal analysis first (in other words, do a modal extraction, as you mentioned). Or you can do a full harmonic analysis and it doesn't need modal extraction.
Using transient analysis only and apply a sinusoidal acceleration boundary should also work, but it will take much longer to run. However, in the transient analysis(without MSUP) you will be able to apply nonlinearities. If you want to simulate any nonlinearity, you should go with transient analysis (without MSUP) and it will provide different results from harmonic analysis.