I betting that "widget" needs an entirely different number, and "gizmo" wants to be called yet another number. While what you're renumbering to has structure and logic it doesn't bear any relationship to any part of the original generic filename.
If you have a list of the new and old names then you need to create a program to do the renaming. The tough part occurs when it comes to getting any assemblies renamed because you want to get all the newly named components to be associative with the new assembly number.
There may be only one assembly, not too large, that you have to do this way. Then assuming you have a list of the is/was names then using windows I'd create a command line batch job to rename the list of files, including assemblies, (in unix a similar script file would do the job). That would save a lot of typing. The part that will take some time is that you'll have to open the assembly in UG and substitute each component with the newly named version, (or use open component as).
If you have a really large amount of renaming, and/or an ongoing need to do this sort of thing then hopefully somebody will have a program than does what you need.
If such a program exists I hope we can track down a copy because many of us have had these sorts of problems, and I want a copy too.....
Regards
Hudson