Let me reiterate. Updating the OS seldom deletes or damages your data, but until someone is able to repeal Murphey's Law there is a minute but finite chance of data loss. The fact you have your RDA and a current Time Machine backup is arguably the best protection you can have.
  1. Reinstalling the OS is the ONLY way to restore the Recovery Drive to your HD and restoring the Recovery Drive. I cannot personally verify this but that may require installation on a clean HD(?)
  2. Given you have a Time Machine backup even that should not cause you to lose any data — it will just take a few hours longer to complete the restore.
    • NOTE: This requires installation of the OS not restoring the OS from the Time Machine backup.
  3. Unless you can find a disk copy of the El Capitan installer you will have to have broadband internet access to install or reinstall your OS. frown

Don't underestimate yourself. You already went through most of this back in 2013.


"All you've got to do is own up to your ignorance
honestly, and you'll find people who are eager to
fill your head with information"
--Walt Disney