The course of this thread has me thinking that there are four separate situations that each of which should be recognized and addressed: troubleshooting in the field, short-term programming modifications, long-term programming modifications, and programming practice.
For troubleshooting in the field, I agree with Bernie and have nothing more to add.
For short-term programming modifications - those ONLY USED to get the machine back up and running in the shortest possible time - you could simply parallel the coil of O:5/30 with the coil for O:5/28 and leave the other 10 instances alone. Of course you want to document this thoroughly and make sure that someone follows up with long-term programming changes when time allows.
For long-term programming modifications, I would do as operaghost suggests and do an offline search-and-replace and then download to the PLC. You need to be sure start with a copy of your most-current program before doing this. Also be sure you have a back-up of the existing program in case something goes wrong.
And finally for programming practice, while jemcneil has described a good technique for the use of aliases, there is another technique that, had it been used, would have prevented the need for all of this; the use of internal tags rather than referencing physical I/O throughout the program. Because field I/O often end up being different than originally designed, I like to have a single rung for each individual input and output that corresponds to an unique internal bit (or register) in the PLC and then use that internal bit (or register) instead of the physical I/O throughout the program. Then, in the event that a wiring change is required, as described by the OP, the program only has to be modified in one place.
Not only does this allow for quick and long-term on-line programming changes, it gives me as the programmer the ability to write my code well in advance of the machine being built, makes I/O checks much faster, and makes programs between similar machines more standardized.
Just my thoughts.
Steve