I am wondering why, still, there is not a feature in Rstudio to search all files in the current project (package) and replace a given text!? Or maybe there is one and I am not aware of!
ctrl+shift+f only finds in all files without replacement.
ctrl+shift+j (or ctrl+f) finds and replaces in the current file.
This is now possible with the 1.3 version of RStudio. You can learn more at https://blog.rstudio.com/2020/03/17/rstudio-1-3-the-little-things/.