control click and copy the clip that you want to insert or use to replace the original clip. Move to the clip in your sequence and control click > paste attributes. A box will appear asking you which options you want to paste. The first option under Video should be content. This will replace the clip in the sequence with the clip in the browser and retain all other attributes, such as keyframes. You might want to load the new clip into the browser to set you desired in point, otherwise the paste will use the clips default in point.
Repeat for all clips the client wants replaced.