Also, when if do a find for your datasetname-to-be-changed you could then do
* tells the editor to use the previous find text (from either find or change).
If you don't put "all" on the end of the change but want to do them one at a time, you can
for each line. Look at RFIND and RCHANGE as well. Useful on function keys if not there already.
Or if you do one change correctly and want then to do all the rest, you can
Full procedure might be
c * new-long-datasetname
verify that the change is correct, fixing as necessary, then
c * * all
It is well worth checking all of this out in the online help/tutoria for the editor. Find and Change are very powerful, if you are aware of what you can do with them.
Edit: I keep forgetting to add that you could also make a little editor macro if this is a common task for you.