If I am selected for the program and have a portion of my sidewalk approved for City cost-sharing, but want additional work done at my own cost (e.g. driveway replacement, etc.), does it also need to be done at prevailing wage rates?

Yes, if you are selected for the program and have any repairs which the City will be cost-sharing in, then any additional requested work at the same address must be done under prevailing wage rates as well.