A top drive system with a plurality of top drive modules, which are configured to be quickly exchanged. The top drive modules may include any or all of the following: a main body module, a gearbox module, a drive motor module, a pipe handler module, an upper fluid module, a lower well control valve module, a block interface module, a retract system interface frame module, a cooling system module, a work platform guard module, and a quill saver sub module. Alternatively, the top drive may comprise a first top drive and a second top drive which are configured to be quickly exchanged.